/*
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */

/** \file
 * \ingroup bmesh
 *
 * BM mesh level functions.
 */

#include "MEM_guardedalloc.h"

#include "DNA_listBase.h"
#include "DNA_scene_types.h"

#include "BLI_bitmap.h"
#include "BLI_linklist_stack.h"
#include "BLI_listbase.h"
#include "BLI_math.h"
#include "BLI_stack.h"
#include "BLI_task.h"
#include "BLI_utildefines.h"

#include "BKE_editmesh.h"
#include "BKE_mesh.h"
#include "BKE_multires.h"

#include "atomic_ops.h"

#include "intern/bmesh_private.h"

/* used as an extern, defined in bmesh.h */
const BMAllocTemplate bm_mesh_allocsize_default = {512, 1024, 2048, 512};
const BMAllocTemplate bm_mesh_chunksize_default = {512, 1024, 2048, 512};

static void bm_mempool_init_ex(const BMAllocTemplate *allocsize,
                               const bool use_toolflags,
                               BLI_mempool **r_vpool,
                               BLI_mempool **r_epool,
                               BLI_mempool **r_lpool,
                               BLI_mempool **r_fpool)
{
  size_t vert_size, edge_size, loop_size, face_size;

  if (use_toolflags == true) {
    vert_size = sizeof(BMVert_OFlag);
    edge_size = sizeof(BMEdge_OFlag);
    loop_size = sizeof(BMLoop);
    face_size = sizeof(BMFace_OFlag);
  }
  else {
    vert_size = sizeof(BMVert);
    edge_size = sizeof(BMEdge);
    loop_size = sizeof(BMLoop);
    face_size = sizeof(BMFace);
  }

  if (r_vpool) {
    *r_vpool = BLI_mempool_create(
        vert_size, allocsize->totvert, bm_mesh_chunksize_default.totvert, BLI_MEMPOOL_ALLOW_ITER);
  }
  if (r_epool) {
    *r_epool = BLI_mempool_create(
        edge_size, allocsize->totedge, bm_mesh_chunksize_default.totedge, BLI_MEMPOOL_ALLOW_ITER);
  }
  if (r_lpool) {
    *r_lpool = BLI_mempool_create(
        loop_size, allocsize->totloop, bm_mesh_chunksize_default.totloop, BLI_MEMPOOL_NOP);
  }
  if (r_fpool) {
    *r_fpool = BLI_mempool_create(
        face_size, allocsize->totface, bm_mesh_chunksize_default.totface, BLI_MEMPOOL_ALLOW_ITER);
  }
}

static void bm_mempool_init(BMesh *bm, const BMAllocTemplate *allocsize, const bool use_toolflags)
{
  bm_mempool_init_ex(allocsize, use_toolflags, &bm->vpool, &bm->epool, &bm->lpool, &bm->fpool);

#ifdef USE_BMESH_HOLES
  bm->looplistpool = BLI_mempool_create(sizeof(BMLoopList), 512, 512, BLI_MEMPOOL_NOP);
#endif
}

void BM_mesh_elem_toolflags_ensure(BMesh *bm)
{
  BLI_assert(bm->use_toolflags);

  if (bm->vtoolflagpool && bm->etoolflagpool && bm->ftoolflagpool) {
    return;
  }

  bm->vtoolflagpool = BLI_mempool_create(sizeof(BMFlagLayer), bm->totvert, 512, BLI_MEMPOOL_NOP);
  bm->etoolflagpool = BLI_mempool_create(sizeof(BMFlagLayer), bm->totedge, 512, BLI_MEMPOOL_NOP);
  bm->ftoolflagpool = BLI_mempool_create(sizeof(BMFlagLayer), bm->totface, 512, BLI_MEMPOOL_NOP);

  BMIter iter;
  BMVert_OFlag *v_olfag;
  BLI_mempool *toolflagpool = bm->vtoolflagpool;
  BM_ITER_MESH (v_olfag, &iter, bm, BM_VERTS_OF_MESH) {
    v_olfag->oflags = BLI_mempool_calloc(toolflagpool);
  }

  BMEdge_OFlag *e_olfag;
  toolflagpool = bm->etoolflagpool;
  BM_ITER_MESH (e_olfag, &iter, bm, BM_EDGES_OF_MESH) {
    e_olfag->oflags = BLI_mempool_calloc(toolflagpool);
  }

  BMFace_OFlag *f_olfag;
  toolflagpool = bm->ftoolflagpool;
  BM_ITER_MESH (f_olfag, &iter, bm, BM_FACES_OF_MESH) {
    f_olfag->oflags = BLI_mempool_calloc(toolflagpool);
  }

  bm->totflags = 1;
}

void BM_mesh_elem_toolflags_clear(BMesh *bm)
{
  if (bm->vtoolflagpool) {
    BLI_mempool_destroy(bm->vtoolflagpool);
    bm->vtoolflagpool = NULL;
  }
  if (bm->etoolflagpool) {
    BLI_mempool_destroy(bm->etoolflagpool);
    bm->etoolflagpool = NULL;
  }
  if (bm->ftoolflagpool) {
    BLI_mempool_destroy(bm->ftoolflagpool);
    bm->ftoolflagpool = NULL;
  }
}

/**
 * \brief BMesh Make Mesh
 *
 * Allocates a new BMesh structure.
 *
 * \return The New bmesh
 *
 * \note ob is needed by multires
 */
BMesh *BM_mesh_create(const BMAllocTemplate *allocsize, const struct BMeshCreateParams *params)
{
  /* allocate the structure */
  BMesh *bm = MEM_callocN(sizeof(BMesh), __func__);

  /* allocate the memory pools for the mesh elements */
  bm_mempool_init(bm, allocsize, params->use_toolflags);

  /* allocate one flag pool that we don't get rid of. */
  bm->use_toolflags = params->use_toolflags;
  bm->toolflag_index = 0;
  bm->totflags = 0;

  CustomData_reset(&bm->vdata);
  CustomData_reset(&bm->edata);
  CustomData_reset(&bm->ldata);
  CustomData_reset(&bm->pdata);

  return bm;
}

/**
 * \brief BMesh Free Mesh Data
 *
 * Frees a BMesh structure.
 *
 * \note frees mesh, but not actual BMesh struct
 */
void BM_mesh_data_free(BMesh *bm)
{
  BMVert *v;
  BMEdge *e;
  BMLoop *l;
  BMFace *f;

  BMIter iter;
  BMIter itersub;

  const bool is_ldata_free = CustomData_bmesh_has_free(&bm->ldata);
  const bool is_pdata_free = CustomData_bmesh_has_free(&bm->pdata);

  /* Check if we have to call free, if not we can avoid a lot of looping */
  if (CustomData_bmesh_has_free(&(bm->vdata))) {
    BM_ITER_MESH (v, &iter, bm, BM_VERTS_OF_MESH) {
      CustomData_bmesh_free_block(&(bm->vdata), &(v->head.data));
    }
  }
  if (CustomData_bmesh_has_free(&(bm->edata))) {
    BM_ITER_MESH (e, &iter, bm, BM_EDGES_OF_MESH) {
      CustomData_bmesh_free_block(&(bm->edata), &(e->head.data));
    }
  }

  if (is_ldata_free || is_pdata_free) {
    BM_ITER_MESH (f, &iter, bm, BM_FACES_OF_MESH) {
      if (is_pdata_free) {
        CustomData_bmesh_free_block(&(bm->pdata), &(f->head.data));
      }
      if (is_ldata_free) {
        BM_ITER_ELEM (l, &itersub, f, BM_LOOPS_OF_FACE) {
          CustomData_bmesh_free_block(&(bm->ldata), &(l->head.data));
        }
      }
    }
  }

  /* Free custom data pools, This should probably go in CustomData_free? */
  if (bm->vdata.totlayer) {
    BLI_mempool_destroy(bm->vdata.pool);
  }
  if (bm->edata.totlayer) {
    BLI_mempool_destroy(bm->edata.pool);
  }
  if (bm->ldata.totlayer) {
    BLI_mempool_destroy(bm->ldata.pool);
  }
  if (bm->pdata.totlayer) {
    BLI_mempool_destroy(bm->pdata.pool);
  }

  /* free custom data */
  CustomData_free(&bm->vdata, 0);
  CustomData_free(&bm->edata, 0);
  CustomData_free(&bm->ldata, 0);
  CustomData_free(&bm->pdata, 0);

  /* destroy element pools */
  BLI_mempool_destroy(bm->vpool);
  BLI_mempool_destroy(bm->epool);
  BLI_mempool_destroy(bm->lpool);
  BLI_mempool_destroy(bm->fpool);

  if (bm->vtable) {
    MEM_freeN(bm->vtable);
  }
  if (bm->etable) {
    MEM_freeN(bm->etable);
  }
  if (bm->ftable) {
    MEM_freeN(bm->ftable);
  }

  /* destroy flag pool */
  BM_mesh_elem_toolflags_clear(bm);

#ifdef USE_BMESH_HOLES
  BLI_mempool_destroy(bm->looplistpool);
#endif

  BLI_freelistN(&bm->selected);

  if (bm->lnor_spacearr) {
    BKE_lnor_spacearr_free(bm->lnor_spacearr);
    MEM_freeN(bm->lnor_spacearr);
  }

  BMO_error_clear(bm);
}

/**
 * \brief BMesh Clear Mesh
 *
 * Clear all data in bm
 */
void BM_mesh_clear(BMesh *bm)
{
  const bool use_toolflags = bm->use_toolflags;

  /* free old mesh */
  BM_mesh_data_free(bm);
  memset(bm, 0, sizeof(BMesh));

  /* allocate the memory pools for the mesh elements */
  bm_mempool_init(bm, &bm_mesh_allocsize_default, use_toolflags);

  bm->use_toolflags = use_toolflags;
  bm->toolflag_index = 0;
  bm->totflags = 0;

  CustomData_reset(&bm->vdata);
  CustomData_reset(&bm->edata);
  CustomData_reset(&bm->ldata);
  CustomData_reset(&bm->pdata);
}

/**
 * \brief BMesh Free Mesh
 *
 * Frees a BMesh data and its structure.
 */
void BM_mesh_free(BMesh *bm)
{
  BM_mesh_data_free(bm);

  if (bm->py_handle) {
    /* keep this out of 'BM_mesh_data_free' because we want python
     * to be able to clear the mesh and maintain access. */
    bpy_bm_generic_invalidate(bm->py_handle);
    bm->py_handle = NULL;
  }

  MEM_freeN(bm);
}

/**
 * Helpers for #BM_mesh_normals_update and #BM_verts_calc_normal_vcos
 */

/* We use that existing internal API flag,
 * assuming no other tool using it would run concurrently to clnors editing. */
#define BM_LNORSPACE_UPDATE _FLAG_MF

typedef struct BMEdgesCalcVectorsData {
  /* Read-only data. */
  const float (*vcos)[3];

  /* Read-write data, but no need to protect it, no concurrency to fear here. */
  float (*edgevec)[3];
} BMEdgesCalcVectorsData;

static void mesh_edges_calc_vectors_cb(void *userdata, MempoolIterData *mp_e)
{
  BMEdgesCalcVectorsData *data = userdata;
  BMEdge *e = (BMEdge *)mp_e;

  if (e->l) {
    const float *v1_co = data->vcos ? data->vcos[BM_elem_index_get(e->v1)] : e->v1->co;
    const float *v2_co = data->vcos ? data->vcos[BM_elem_index_get(e->v2)] : e->v2->co;
    sub_v3_v3v3(data->edgevec[BM_elem_index_get(e)], v2_co, v1_co);
    normalize_v3(data->edgevec[BM_elem_index_get(e)]);
  }
  else {
    /* the edge vector will not be needed when the edge has no radial */
  }
}

static void bm_mesh_edges_calc_vectors(BMesh *bm, float (*edgevec)[3], const float (*vcos)[3])
{
  BM_mesh_elem_index_ensure(bm, BM_EDGE | (vcos ? BM_VERT : 0));

  BMEdgesCalcVectorsData data = {
      .vcos = vcos,
      .edgevec = edgevec,
  };

  BM_iter_parallel(
      bm, BM_EDGES_OF_MESH, mesh_edges_calc_vectors_cb, &data, bm->totedge >= BM_OMP_LIMIT);
}

typedef struct BMVertsCalcNormalsData {
  /* Read-only data. */
  const float (*fnos)[3];
  const float (*edgevec)[3];
  const float (*vcos)[3];

  /* Read-write data, protected by an atomic-based fake spin-lock like system. */
  float (*vnos)[3];
} BMVertsCalcNormalsData;

static void mesh_verts_calc_normals_accum_cb(void *userdata, MempoolIterData *mp_f)
{
#define FLT_EQ_NONAN(_fa, _fb) (*((const uint32_t *)&_fa) == *((const uint32_t *)&_fb))

  BMVertsCalcNormalsData *data = userdata;
  BMFace *f = (BMFace *)mp_f;

  const float *f_no = data->fnos ? data->fnos[BM_elem_index_get(f)] : f->no;

  BMLoop *l_first, *l_iter;
  l_iter = l_first = BM_FACE_FIRST_LOOP(f);
  do {
    const float *e1diff, *e2diff;
    float dotprod;
    float fac;

    /* calculate the dot product of the two edges that
     * meet at the loop's vertex */
    e1diff = data->edgevec[BM_elem_index_get(l_iter->prev->e)];
    e2diff = data->edgevec[BM_elem_index_get(l_iter->e)];
    dotprod = dot_v3v3(e1diff, e2diff);

    /* edge vectors are calculated from e->v1 to e->v2, so
     * adjust the dot product if one but not both loops
     * actually runs from from e->v2 to e->v1 */
    if ((l_iter->prev->e->v1 == l_iter->prev->v) ^ (l_iter->e->v1 == l_iter->v)) {
      dotprod = -dotprod;
    }

    fac = saacos(-dotprod);

    if (fac != fac) { /* NAN detection. */
      /* Degenerated case, nothing to do here, just ignore that vertex. */
      continue;
    }

    /* accumulate weighted face normal into the vertex's normal */
    float *v_no = data->vnos ? data->vnos[BM_elem_index_get(l_iter->v)] : l_iter->v->no;

    /* This block is a lockless threadsafe madd_v3_v3fl.
     * It uses the first float of the vector as a sort of cheap spin-lock,
     * assuming FLT_MAX is a safe 'illegal' value that cannot be set here otherwise.
     * It also assumes that collisions between threads are highly unlikely,
     * else performances would be quite bad here. */
    float virtual_lock = v_no[0];
    while (true) {
      /* This loops until following conditions are met:
       *   - v_no[0] has same value as virtual_lock (i.e. it did not change since last try).
       *   - v_no[0] was not FLT_MAX, i.e. it was not locked by another thread.
       */
      const float vl = atomic_cas_float(&v_no[0], virtual_lock, FLT_MAX);
      if (FLT_EQ_NONAN(vl, virtual_lock) && vl != FLT_MAX) {
        break;
      }
      virtual_lock = vl;
    }
    BLI_assert(v_no[0] == FLT_MAX);
    /* Now we own that normal value, and can change it.
     * But first scalar of the vector must not be changed yet, it's our lock! */
    virtual_lock += f_no[0] * fac;
    v_no[1] += f_no[1] * fac;
    v_no[2] += f_no[2] * fac;
    /* Second atomic operation to 'release'
     * our lock on that vector and set its first scalar value. */
    /* Note that we do not need to loop here, since we 'locked' v_no[0],
     * nobody should have changed it in the mean time. */
    virtual_lock = atomic_cas_float(&v_no[0], FLT_MAX, virtual_lock);
    BLI_assert(virtual_lock == FLT_MAX);

  } while ((l_iter = l_iter->next) != l_first);

#undef FLT_EQ_NONAN
}

static void mesh_verts_calc_normals_normalize_cb(void *userdata, MempoolIterData *mp_v)
{
  BMVertsCalcNormalsData *data = userdata;
  BMVert *v = (BMVert *)mp_v;

  float *v_no = data->vnos ? data->vnos[BM_elem_index_get(v)] : v->no;
  if (UNLIKELY(normalize_v3(v_no) == 0.0f)) {
    const float *v_co = data->vcos ? data->vcos[BM_elem_index_get(v)] : v->co;
    normalize_v3_v3(v_no, v_co);
  }
}

static void bm_mesh_verts_calc_normals(BMesh *bm,
                                       const float (*edgevec)[3],
                                       const float (*fnos)[3],
                                       const float (*vcos)[3],
                                       float (*vnos)[3])
{
  BM_mesh_elem_index_ensure(bm, (BM_EDGE | BM_FACE) | ((vnos || vcos) ? BM_VERT : 0));

  BMVertsCalcNormalsData data = {
      .fnos = fnos,
      .edgevec = edgevec,
      .vcos = vcos,
      .vnos = vnos,
  };

  BM_iter_parallel(
      bm, BM_FACES_OF_MESH, mesh_verts_calc_normals_accum_cb, &data, bm->totface >= BM_OMP_LIMIT);

  /* normalize the accumulated vertex normals */
  BM_iter_parallel(bm,
                   BM_VERTS_OF_MESH,
                   mesh_verts_calc_normals_normalize_cb,
                   &data,
                   bm->totvert >= BM_OMP_LIMIT);
}

static void mesh_faces_calc_normals_cb(void *UNUSED(userdata), MempoolIterData *mp_f)
{
  BMFace *f = (BMFace *)mp_f;

  BM_face_normal_update(f);
}

/**
 * \brief BMesh Compute Normals
 *
 * Updates the normals of a mesh.
 */
void BM_mesh_normals_update(BMesh *bm)
{
  float(*edgevec)[3] = MEM_mallocN(sizeof(*edgevec) * bm->totedge, __func__);

  /* Parallel mempool iteration does not allow to generate indices inline anymore... */
  BM_mesh_elem_index_ensure(bm, (BM_EDGE | BM_FACE));

  /* calculate all face normals */
  BM_iter_parallel(
      bm, BM_FACES_OF_MESH, mesh_faces_calc_normals_cb, NULL, bm->totface >= BM_OMP_LIMIT);

  /* Zero out vertex normals */
  BMIter viter;
  BMVert *v;
  int i;

  BM_ITER_MESH_INDEX (v, &viter, bm, BM_VERTS_OF_MESH, i) {
    BM_elem_index_set(v, i); /* set_inline */
    zero_v3(v->no);
  }
  bm->elem_index_dirty &= ~BM_VERT;

  /* Compute normalized direction vectors for each edge.
   * Directions will be used for calculating the weights of the face normals on the vertex normals.
   */
  bm_mesh_edges_calc_vectors(bm, edgevec, NULL);

  /* Add weighted face normals to vertices, and normalize vert normals. */
  bm_mesh_verts_calc_normals(bm, (const float(*)[3])edgevec, NULL, NULL, NULL);
  MEM_freeN(edgevec);
}

/**
 * \brief BMesh Compute Normals from/to external data.
 *
 * Computes the vertex normals of a mesh into vnos,
 * using given vertex coordinates (vcos) and polygon normals (fnos).
 */
void BM_verts_calc_normal_vcos(BMesh *bm,
                               const float (*fnos)[3],
                               const float (*vcos)[3],
                               float (*vnos)[3])
{
  float(*edgevec)[3] = MEM_mallocN(sizeof(*edgevec) * bm->totedge, __func__);

  /* Compute normalized direction vectors for each edge.
   * Directions will be used for calculating the weights of the face normals on the vertex normals.
   */
  bm_mesh_edges_calc_vectors(bm, edgevec, vcos);

  /* Add weighted face normals to vertices, and normalize vert normals. */
  bm_mesh_verts_calc_normals(bm, (const float(*)[3])edgevec, fnos, vcos, vnos);
  MEM_freeN(edgevec);
}

/**
 * Helpers for #BM_mesh_loop_normals_update and #BM_loops_calc_normal_vcos
 */
static void bm_mesh_edges_sharp_tag(BMesh *bm,
                                    const float (*vnos)[3],
                                    const float (*fnos)[3],
                                    float (*r_lnos)[3],
                                    const float split_angle,
                                    const bool do_sharp_edges_tag)
{
  BMIter eiter;
  BMEdge *e;
  int i;

  const bool check_angle = (split_angle < (float)M_PI);
  const float split_angle_cos = check_angle ? cosf(split_angle) : -1.0f;

  {
    char htype = BM_VERT | BM_LOOP;
    if (fnos) {
      htype |= BM_FACE;
    }
    BM_mesh_elem_index_ensure(bm, htype);
  }

  /* This first loop checks which edges are actually smooth,
   * and pre-populate lnos with vnos (as if they were all smooth). */
  BM_ITER_MESH_INDEX (e, &eiter, bm, BM_EDGES_OF_MESH, i) {
    BMLoop *l_a, *l_b;

    BM_elem_index_set(e, i);              /* set_inline */
    BM_elem_flag_disable(e, BM_ELEM_TAG); /* Clear tag (means edge is sharp). */

    /* An edge with only two loops, might be smooth... */
    if (BM_edge_loop_pair(e, &l_a, &l_b)) {
      bool is_angle_smooth = true;
      if (check_angle) {
        const float *no_a = fnos ? fnos[BM_elem_index_get(l_a->f)] : l_a->f->no;
        const float *no_b = fnos ? fnos[BM_elem_index_get(l_b->f)] : l_b->f->no;
        is_angle_smooth = (dot_v3v3(no_a, no_b) >= split_angle_cos);
      }

      /* We only tag edges that are *really* smooth:
       * If the angle between both its polys' normals is below split_angle value,
       * and it is tagged as such,
       * and both its faces are smooth,
       * and both its faces have compatible (non-flipped) normals,
       * i.e. both loops on the same edge do not share the same vertex.
       */
      if (BM_elem_flag_test(e, BM_ELEM_SMOOTH) && BM_elem_flag_test(l_a->f, BM_ELEM_SMOOTH) &&
          BM_elem_flag_test(l_b->f, BM_ELEM_SMOOTH) && l_a->v != l_b->v) {
        if (is_angle_smooth) {
          const float *no;
          BM_elem_flag_enable(e, BM_ELEM_TAG);

          /* linked vertices might be fully smooth, copy their normals to loop ones. */
          if (r_lnos) {
            no = vnos ? vnos[BM_elem_index_get(l_a->v)] : l_a->v->no;
            copy_v3_v3(r_lnos[BM_elem_index_get(l_a)], no);
            no = vnos ? vnos[BM_elem_index_get(l_b->v)] : l_b->v->no;
            copy_v3_v3(r_lnos[BM_elem_index_get(l_b)], no);
          }
        }
        else if (do_sharp_edges_tag) {
          /* Note that we do not care about the other sharp-edge cases
           * (sharp poly, non-manifold edge, etc.),
           * only tag edge as sharp when it is due to angle threshold. */
          BM_elem_flag_disable(e, BM_ELEM_SMOOTH);
        }
      }
    }
  }

  bm->elem_index_dirty &= ~BM_EDGE;
}

/**
 * Check whether given loop is part of an unknown-so-far cyclic smooth fan, or not.
 * Needed because cyclic smooth fans have no obvious 'entry point',
 * and yet we need to walk them once, and only once.
 */
bool BM_loop_check_cyclic_smooth_fan(BMLoop *l_curr)
{
  BMLoop *lfan_pivot_next = l_curr;
  BMEdge *e_next = l_curr->e;

  BLI_assert(!BM_elem_flag_test(lfan_pivot_next, BM_ELEM_TAG));
  BM_elem_flag_enable(lfan_pivot_next, BM_ELEM_TAG);

  while (true) {
    /* Much simpler than in sibling code with basic Mesh data! */
    lfan_pivot_next = BM_vert_step_fan_loop(lfan_pivot_next, &e_next);

    if (!lfan_pivot_next || !BM_elem_flag_test(e_next, BM_ELEM_TAG)) {
      /* Sharp loop/edge, so not a cyclic smooth fan... */
      return false;
    }
    /* Smooth loop/edge... */
    else if (BM_elem_flag_test(lfan_pivot_next, BM_ELEM_TAG)) {
      if (lfan_pivot_next == l_curr) {
        /* We walked around a whole cyclic smooth fan
         * without finding any already-processed loop,
         * means we can use initial l_curr/l_prev edge as start for this smooth fan. */
        return true;
      }
      /* ... already checked in some previous looping, we can abort. */
      return false;
    }
    else {
      /* ... we can skip it in future, and keep checking the smooth fan. */
      BM_elem_flag_enable(lfan_pivot_next, BM_ELEM_TAG);
    }
  }
}

/**
 * BMesh version of BKE_mesh_normals_loop_split() in mesh_evaluate.c
 * Will use first clnors_data array, and fallback to cd_loop_clnors_offset
 * (use NULL and -1 to not use clnors).
 */
static void bm_mesh_loops_calc_normals(BMesh *bm,
                                       const float (*vcos)[3],
                                       const float (*fnos)[3],
                                       float (*r_lnos)[3],
                                       MLoopNorSpaceArray *r_lnors_spacearr,
                                       short (*clnors_data)[2],
                                       const int cd_loop_clnors_offset,
                                       const bool do_rebuild)
{
  BMIter fiter;
  BMFace *f_curr;
  const bool has_clnors = clnors_data || (cd_loop_clnors_offset != -1);

  MLoopNorSpaceArray _lnors_spacearr = {NULL};

  /* Temp normal stack. */
  BLI_SMALLSTACK_DECLARE(normal, float *);
  /* Temp clnors stack. */
  BLI_SMALLSTACK_DECLARE(clnors, short *);
  /* Temp edge vectors stack, only used when computing lnor spacearr. */
  BLI_Stack *edge_vectors = NULL;

  {
    char htype = 0;
    if (vcos) {
      htype |= BM_VERT;
    }
    /* Face/Loop indices are set inline below. */
    BM_mesh_elem_index_ensure(bm, htype);
  }

  if (!r_lnors_spacearr && has_clnors) {
    /* We need to compute lnor spacearr if some custom lnor data are given to us! */
    r_lnors_spacearr = &_lnors_spacearr;
  }
  if (r_lnors_spacearr) {
    BKE_lnor_spacearr_init(r_lnors_spacearr, bm->totloop, MLNOR_SPACEARR_BMLOOP_PTR);
    edge_vectors = BLI_stack_new(sizeof(float[3]), __func__);
  }

  /* Clear all loops' tags (means none are to be skipped for now). */
  int index_face, index_loop = 0;
  BM_ITER_MESH_INDEX (f_curr, &fiter, bm, BM_FACES_OF_MESH, index_face) {
    BMLoop *l_curr, *l_first;

    BM_elem_index_set(f_curr, index_face); /* set_inline */

    l_curr = l_first = BM_FACE_FIRST_LOOP(f_curr);
    do {
      BM_elem_index_set(l_curr, index_loop++); /* set_inline */
      BM_elem_flag_disable(l_curr, BM_ELEM_TAG);
    } while ((l_curr = l_curr->next) != l_first);
  }
  bm->elem_index_dirty &= ~(BM_FACE | BM_LOOP);

  /* We now know edges that can be smoothed (they are tagged),
   * and edges that will be hard (they aren't).
   * Now, time to generate the normals.
   */
  BM_ITER_MESH (f_curr, &fiter, bm, BM_FACES_OF_MESH) {
    BMLoop *l_curr, *l_first;

    l_curr = l_first = BM_FACE_FIRST_LOOP(f_curr);
    do {
      if (do_rebuild && !BM_ELEM_API_FLAG_TEST(l_curr, BM_LNORSPACE_UPDATE) &&
          !(bm->spacearr_dirty & BM_SPACEARR_DIRTY_ALL)) {
        continue;
      }
      /* A smooth edge, we have to check for cyclic smooth fan case.
       * If we find a new, never-processed cyclic smooth fan, we can do it now using that loop/edge
       * as 'entry point', otherwise we can skip it. */

      /* Note: In theory, we could make bm_mesh_loop_check_cyclic_smooth_fan() store
       * mlfan_pivot's in a stack, to avoid having to fan again around
       * the vert during actual computation of clnor & clnorspace. However, this would complicate
       * the code, add more memory usage, and
       * BM_vert_step_fan_loop() is quite cheap in term of CPU cycles,
       * so really think it's not worth it. */
      if (BM_elem_flag_test(l_curr->e, BM_ELEM_TAG) &&
          (BM_elem_flag_test(l_curr, BM_ELEM_TAG) || !BM_loop_check_cyclic_smooth_fan(l_curr))) {
      }
      else if (!BM_elem_flag_test(l_curr->e, BM_ELEM_TAG) &&
               !BM_elem_flag_test(l_curr->prev->e, BM_ELEM_TAG)) {
        /* Simple case (both edges around that vertex are sharp in related polygon),
         * this vertex just takes its poly normal.
         */
        const int l_curr_index = BM_elem_index_get(l_curr);
        const float *no = fnos ? fnos[BM_elem_index_get(f_curr)] : f_curr->no;
        copy_v3_v3(r_lnos[l_curr_index], no);

        /* If needed, generate this (simple!) lnor space. */
        if (r_lnors_spacearr) {
          float vec_curr[3], vec_prev[3];
          MLoopNorSpace *lnor_space = BKE_lnor_space_create(r_lnors_spacearr);

          {
            const BMVert *v_pivot = l_curr->v;
            const float *co_pivot = vcos ? vcos[BM_elem_index_get(v_pivot)] : v_pivot->co;
            const BMVert *v_1 = BM_edge_other_vert(l_curr->e, v_pivot);
            const float *co_1 = vcos ? vcos[BM_elem_index_get(v_1)] : v_1->co;
            const BMVert *v_2 = BM_edge_other_vert(l_curr->prev->e, v_pivot);
            const float *co_2 = vcos ? vcos[BM_elem_index_get(v_2)] : v_2->co;

            sub_v3_v3v3(vec_curr, co_1, co_pivot);
            normalize_v3(vec_curr);
            sub_v3_v3v3(vec_prev, co_2, co_pivot);
            normalize_v3(vec_prev);
          }

          BKE_lnor_space_define(lnor_space, r_lnos[l_curr_index], vec_curr, vec_prev, NULL);
          /* We know there is only one loop in this space,
           * no need to create a linklist in this case... */
          BKE_lnor_space_add_loop(r_lnors_spacearr, lnor_space, l_curr_index, l_curr, true);

          if (has_clnors) {
            short(*clnor)[2] = clnors_data ? &clnors_data[l_curr_index] :
                                             BM_ELEM_CD_GET_VOID_P(l_curr, cd_loop_clnors_offset);
            BKE_lnor_space_custom_data_to_normal(lnor_space, *clnor, r_lnos[l_curr_index]);
          }
        }
      }
      /* We *do not need* to check/tag loops as already computed!
       * Due to the fact a loop only links to one of its two edges,
       * a same fan *will never be walked more than once!*
       * Since we consider edges having neighbor faces with inverted (flipped) normals as sharp,
       * we are sure that no fan will be skipped, even only considering the case
       * (sharp curr_edge, smooth prev_edge), and not the alternative
       * (smooth curr_edge, sharp prev_edge).
       * All this due/thanks to link between normals and loop ordering.
       */
      else {
        /* We have to fan around current vertex, until we find the other non-smooth edge,
         * and accumulate face normals into the vertex!
         * Note in case this vertex has only one sharp edge,
         * this is a waste because the normal is the same as the vertex normal,
         * but I do not see any easy way to detect that (would need to count number of sharp edges
         * per vertex, I doubt the additional memory usage would be worth it, especially as it
         * should not be a common case in real-life meshes anyway).
         */
        BMVert *v_pivot = l_curr->v;
        BMEdge *e_next;
        const BMEdge *e_org = l_curr->e;
        BMLoop *lfan_pivot, *lfan_pivot_next;
        int lfan_pivot_index;
        float lnor[3] = {0.0f, 0.0f, 0.0f};
        float vec_curr[3], vec_next[3], vec_org[3];

        /* We validate clnors data on the fly - cheapest way to do! */
        int clnors_avg[2] = {0, 0};
        short(*clnor_ref)[2] = NULL;
        int clnors_nbr = 0;
        bool clnors_invalid = false;

        const float *co_pivot = vcos ? vcos[BM_elem_index_get(v_pivot)] : v_pivot->co;

        MLoopNorSpace *lnor_space = r_lnors_spacearr ? BKE_lnor_space_create(r_lnors_spacearr) :
                                                       NULL;

        BLI_assert((edge_vectors == NULL) || BLI_stack_is_empty(edge_vectors));

        lfan_pivot = l_curr;
        lfan_pivot_index = BM_elem_index_get(lfan_pivot);
        e_next = lfan_pivot->e; /* Current edge here, actually! */

        /* Only need to compute previous edge's vector once,
         * then we can just reuse old current one! */
        {
          const BMVert *v_2 = BM_edge_other_vert(e_next, v_pivot);
          const float *co_2 = vcos ? vcos[BM_elem_index_get(v_2)] : v_2->co;

          sub_v3_v3v3(vec_org, co_2, co_pivot);
          normalize_v3(vec_org);
          copy_v3_v3(vec_curr, vec_org);

          if (r_lnors_spacearr) {
            BLI_stack_push(edge_vectors, vec_org);
          }
        }

        while (true) {
          /* Much simpler than in sibling code with basic Mesh data! */
          lfan_pivot_next = BM_vert_step_fan_loop(lfan_pivot, &e_next);
          if (lfan_pivot_next) {
            BLI_assert(lfan_pivot_next->v == v_pivot);
          }
          else {
            /* next edge is non-manifold, we have to find it ourselves! */
            e_next = (lfan_pivot->e == e_next) ? lfan_pivot->prev->e : lfan_pivot->e;
          }

          /* Compute edge vector.
           * NOTE: We could pre-compute those into an array, in the first iteration,
           * instead of computing them twice (or more) here.
           * However, time gained is not worth memory and time lost,
           * given the fact that this code should not be called that much in real-life meshes.
           */
          {
            const BMVert *v_2 = BM_edge_other_vert(e_next, v_pivot);
            const float *co_2 = vcos ? vcos[BM_elem_index_get(v_2)] : v_2->co;

            sub_v3_v3v3(vec_next, co_2, co_pivot);
            normalize_v3(vec_next);
          }

          {
            /* Code similar to accumulate_vertex_normals_poly_v3. */
            /* Calculate angle between the two poly edges incident on this vertex. */
            const BMFace *f = lfan_pivot->f;
            const float fac = saacos(dot_v3v3(vec_next, vec_curr));
            const float *no = fnos ? fnos[BM_elem_index_get(f)] : f->no;
            /* Accumulate */
            madd_v3_v3fl(lnor, no, fac);

            if (has_clnors) {
              /* Accumulate all clnors, if they are not all equal we have to fix that! */
              short(*clnor)[2] = clnors_data ?
                                     &clnors_data[lfan_pivot_index] :
                                     BM_ELEM_CD_GET_VOID_P(lfan_pivot, cd_loop_clnors_offset);
              if (clnors_nbr) {
                clnors_invalid |= ((*clnor_ref)[0] != (*clnor)[0] ||
                                   (*clnor_ref)[1] != (*clnor)[1]);
              }
              else {
                clnor_ref = clnor;
              }
              clnors_avg[0] += (*clnor)[0];
              clnors_avg[1] += (*clnor)[1];
              clnors_nbr++;
              /* We store here a pointer to all custom lnors processed. */
              BLI_SMALLSTACK_PUSH(clnors, (short *)*clnor);
            }
          }

          /* We store here a pointer to all loop-normals processed. */
          BLI_SMALLSTACK_PUSH(normal, (float *)r_lnos[lfan_pivot_index]);

          if (r_lnors_spacearr) {
            /* Assign current lnor space to current 'vertex' loop. */
            BKE_lnor_space_add_loop(
                r_lnors_spacearr, lnor_space, lfan_pivot_index, lfan_pivot, false);
            if (e_next != e_org) {
              /* We store here all edges-normalized vectors processed. */
              BLI_stack_push(edge_vectors, vec_next);
            }
          }

          if (!BM_elem_flag_test(e_next, BM_ELEM_TAG) || (e_next == e_org)) {
            /* Next edge is sharp, we have finished with this fan of faces around this vert! */
            break;
          }

          /* Copy next edge vector to current one. */
          copy_v3_v3(vec_curr, vec_next);
          /* Next pivot loop to current one. */
          lfan_pivot = lfan_pivot_next;
          lfan_pivot_index = BM_elem_index_get(lfan_pivot);
        }

        {
          float lnor_len = normalize_v3(lnor);

          /* If we are generating lnor spacearr, we can now define the one for this fan. */
          if (r_lnors_spacearr) {
            if (UNLIKELY(lnor_len == 0.0f)) {
              /* Use vertex normal as fallback! */
              copy_v3_v3(lnor, r_lnos[lfan_pivot_index]);
              lnor_len = 1.0f;
            }

            BKE_lnor_space_define(lnor_space, lnor, vec_org, vec_next, edge_vectors);

            if (has_clnors) {
              if (clnors_invalid) {
                short *clnor;

                clnors_avg[0] /= clnors_nbr;
                clnors_avg[1] /= clnors_nbr;
                /* Fix/update all clnors of this fan with computed average value. */

                /* Prints continuously when merge custom normals, so commenting. */
                /* printf("Invalid clnors in this fan!\n"); */

                while ((clnor = BLI_SMALLSTACK_POP(clnors))) {
                  // print_v2("org clnor", clnor);
                  clnor[0] = (short)clnors_avg[0];
                  clnor[1] = (short)clnors_avg[1];
                }
                // print_v2("new clnors", clnors_avg);
              }
              else {
                /* We still have to consume the stack! */
                while (BLI_SMALLSTACK_POP(clnors)) {
                  /* pass */
                }
              }
              BKE_lnor_space_custom_data_to_normal(lnor_space, *clnor_ref, lnor);
            }
          }

          /* In case we get a zero normal here, just use vertex normal already set! */
          if (LIKELY(lnor_len != 0.0f)) {
            /* Copy back the final computed normal into all related loop-normals. */
            float *nor;

            while ((nor = BLI_SMALLSTACK_POP(normal))) {
              copy_v3_v3(nor, lnor);
            }
          }
          else {
            /* We still have to consume the stack! */
            while (BLI_SMALLSTACK_POP(normal)) {
              /* pass */
            }
          }
        }

        /* Tag related vertex as sharp, to avoid fanning around it again
         * (in case it was a smooth one). */
        if (r_lnors_spacearr) {
          BM_elem_flag_enable(l_curr->v, BM_ELEM_TAG);
        }
      }
    } while ((l_curr = l_curr->next) != l_first);
  }

  if (r_lnors_spacearr) {
    BLI_stack_free(edge_vectors);
    if (r_lnors_spacearr == &_lnors_spacearr) {
      BKE_lnor_spacearr_free(r_lnors_spacearr);
    }
  }
}

static void bm_mesh_loops_calc_normals_no_autosmooth(BMesh *bm,
                                                     const float (*vnos)[3],
                                                     const float (*fnos)[3],
                                                     float (*r_lnos)[3])
{
  BMIter fiter;
  BMFace *f_curr;

  {
    char htype = BM_LOOP;
    if (vnos) {
      htype |= BM_VERT;
    }
    if (fnos) {
      htype |= BM_FACE;
    }
    BM_mesh_elem_index_ensure(bm, htype);
  }

  BM_ITER_MESH (f_curr, &fiter, bm, BM_FACES_OF_MESH) {
    BMLoop *l_curr, *l_first;
    const bool is_face_flat = !BM_elem_flag_test(f_curr, BM_ELEM_SMOOTH);

    l_curr = l_first = BM_FACE_FIRST_LOOP(f_curr);
    do {
      const float *no = is_face_flat ? (fnos ? fnos[BM_elem_index_get(f_curr)] : f_curr->no) :
                                       (vnos ? vnos[BM_elem_index_get(l_curr->v)] : l_curr->v->no);
      copy_v3_v3(r_lnos[BM_elem_index_get(l_curr)], no);

    } while ((l_curr = l_curr->next) != l_first);
  }
}

#if 0 /* Unused currently */
/**
 * \brief BMesh Compute Loop Normals
 *
 * Updates the loop normals of a mesh.
 * Assumes vertex and face normals are valid (else call BM_mesh_normals_update() first)!
 */
void BM_mesh_loop_normals_update(BMesh *bm,
                                 const bool use_split_normals,
                                 const float split_angle,
                                 float (*r_lnos)[3],
                                 MLoopNorSpaceArray *r_lnors_spacearr,
                                 short (*clnors_data)[2],
                                 const int cd_loop_clnors_offset)
{
  const bool has_clnors = clnors_data || (cd_loop_clnors_offset != -1);

  if (use_split_normals) {
    /* Tag smooth edges and set lnos from vnos when they might be completely smooth...
     * When using custom loop normals, disable the angle feature! */
    bm_mesh_edges_sharp_tag(bm, NULL, NULL, has_clnors ? (float)M_PI : split_angle, r_lnos);

    /* Finish computing lnos by accumulating face normals
     * in each fan of faces defined by sharp edges. */
    bm_mesh_loops_calc_normals(
        bm, NULL, NULL, r_lnos, r_lnors_spacearr, clnors_data, cd_loop_clnors_offset);
  }
  else {
    BLI_assert(!r_lnors_spacearr);
    bm_mesh_loops_calc_normals_no_autosmooth(bm, NULL, NULL, r_lnos);
  }
}
#endif

/**
 * \brief BMesh Compute Loop Normals from/to external data.
 *
 * Compute split normals, i.e. vertex normals associated with each poly (hence 'loop normals').
 * Useful to materialize sharp edges (or non-smooth faces) without actually modifying the geometry
 * (splitting edges).
 */
void BM_loops_calc_normal_vcos(BMesh *bm,
                               const float (*vcos)[3],
                               const float (*vnos)[3],
                               const float (*fnos)[3],
                               const bool use_split_normals,
                               const float split_angle,
                               float (*r_lnos)[3],
                               MLoopNorSpaceArray *r_lnors_spacearr,
                               short (*clnors_data)[2],
                               const int cd_loop_clnors_offset,
                               const bool do_rebuild)
{
  const bool has_clnors = clnors_data || (cd_loop_clnors_offset != -1);

  if (use_split_normals) {
    /* Tag smooth edges and set lnos from vnos when they might be completely smooth...
     * When using custom loop normals, disable the angle feature! */
    bm_mesh_edges_sharp_tag(bm, vnos, fnos, r_lnos, has_clnors ? (float)M_PI : split_angle, false);

    /* Finish computing lnos by accumulating face normals
     * in each fan of faces defined by sharp edges. */
    bm_mesh_loops_calc_normals(
        bm, vcos, fnos, r_lnos, r_lnors_spacearr, clnors_data, cd_loop_clnors_offset, do_rebuild);
  }
  else {
    BLI_assert(!r_lnors_spacearr);
    bm_mesh_loops_calc_normals_no_autosmooth(bm, vnos, fnos, r_lnos);
  }
}

/**
 * Define sharp edges as needed to mimic 'autosmooth' from angle threshold.
 *
 * Used when defining an empty custom loop normals data layer,
 * to keep same shading as with autosmooth!
 */
void BM_edges_sharp_from_angle_set(BMesh *bm, const float split_angle)
{
  if (split_angle >= (float)M_PI) {
    /* Nothing to do! */
    return;
  }

  bm_mesh_edges_sharp_tag(bm, NULL, NULL, NULL, split_angle, true);
}

void BM_lnorspacearr_store(BMesh *bm, float (*r_lnors)[3])
{
  BLI_assert(bm->lnor_spacearr != NULL);

  if (!CustomData_has_layer(&bm->ldata, CD_CUSTOMLOOPNORMAL)) {
    BM_data_layer_add(bm, &bm->ldata, CD_CUSTOMLOOPNORMAL);
  }

  int cd_loop_clnors_offset = CustomData_get_offset(&bm->ldata, CD_CUSTOMLOOPNORMAL);

  BM_loops_calc_normal_vcos(bm,
                            NULL,
                            NULL,
                            NULL,
                            true,
                            M_PI,
                            r_lnors,
                            bm->lnor_spacearr,
                            NULL,
                            cd_loop_clnors_offset,
                            false);
  bm->spacearr_dirty &= ~(BM_SPACEARR_DIRTY | BM_SPACEARR_DIRTY_ALL);
}

#define CLEAR_SPACEARRAY_THRESHOLD(x) ((x) / 2)

void BM_lnorspace_invalidate(BMesh *bm, const bool do_invalidate_all)
{
  if (bm->spacearr_dirty & BM_SPACEARR_DIRTY_ALL) {
    return;
  }
  if (do_invalidate_all || bm->totvertsel > CLEAR_SPACEARRAY_THRESHOLD(bm->totvert)) {
    bm->spacearr_dirty |= BM_SPACEARR_DIRTY_ALL;
    return;
  }
  if (bm->lnor_spacearr == NULL) {
    bm->spacearr_dirty |= BM_SPACEARR_DIRTY_ALL;
    return;
  }

  BMVert *v;
  BMLoop *l;
  BMIter viter, liter;
  /* Note: we could use temp tag of BMItem for that,
   * but probably better not use it in such a low-level func?
   * --mont29 */
  BLI_bitmap *done_verts = BLI_BITMAP_NEW(bm->totvert, __func__);

  BM_mesh_elem_index_ensure(bm, BM_VERT);

  /* When we affect a given vertex, we may affect following smooth fans:
   *     - all smooth fans of said vertex;
   *     - all smooth fans of all immediate loop-neighbors vertices;
   * This can be simplified as 'all loops of selected vertices and their immediate neighbors'
   * need to be tagged for update.
   */
  BM_ITER_MESH (v, &viter, bm, BM_VERTS_OF_MESH) {
    if (BM_elem_flag_test(v, BM_ELEM_SELECT)) {
      BM_ITER_ELEM (l, &liter, v, BM_LOOPS_OF_VERT) {
        BM_ELEM_API_FLAG_ENABLE(l, BM_LNORSPACE_UPDATE);

        /* Note that we only handle unselected neighbor vertices here, main loop will take care of
         * selected ones. */
        if ((!BM_elem_flag_test(l->prev->v, BM_ELEM_SELECT)) &&
            !BLI_BITMAP_TEST(done_verts, BM_elem_index_get(l->prev->v))) {

          BMLoop *l_prev;
          BMIter liter_prev;
          BM_ITER_ELEM (l_prev, &liter_prev, l->prev->v, BM_LOOPS_OF_VERT) {
            BM_ELEM_API_FLAG_ENABLE(l_prev, BM_LNORSPACE_UPDATE);
          }
          BLI_BITMAP_ENABLE(done_verts, BM_elem_index_get(l_prev->v));
        }

        if ((!BM_elem_flag_test(l->next->v, BM_ELEM_SELECT)) &&
            !BLI_BITMAP_TEST(done_verts, BM_elem_index_get(l->next->v))) {

          BMLoop *l_next;
          BMIter liter_next;
          BM_ITER_ELEM (l_next, &liter_next, l->next->v, BM_LOOPS_OF_VERT) {
            BM_ELEM_API_FLAG_ENABLE(l_next, BM_LNORSPACE_UPDATE);
          }
          BLI_BITMAP_ENABLE(done_verts, BM_elem_index_get(l_next->v));
        }
      }

      BLI_BITMAP_ENABLE(done_verts, BM_elem_index_get(v));
    }
  }

  MEM_freeN(done_verts);
  bm->spacearr_dirty |= BM_SPACEARR_DIRTY;
}

void BM_lnorspace_rebuild(BMesh *bm, bool preserve_clnor)
{
  BLI_assert(bm->lnor_spacearr != NULL);

  if (!(bm->spacearr_dirty & (BM_SPACEARR_DIRTY | BM_SPACEARR_DIRTY_ALL))) {
    return;
  }
  BMFace *f;
  BMLoop *l;
  BMIter fiter, liter;

  float(*r_lnors)[3] = MEM_callocN(sizeof(*r_lnors) * bm->totloop, __func__);
  float(*oldnors)[3] = preserve_clnor ? MEM_mallocN(sizeof(*oldnors) * bm->totloop, __func__) :
                                        NULL;

  int cd_loop_clnors_offset = CustomData_get_offset(&bm->ldata, CD_CUSTOMLOOPNORMAL);

  BM_mesh_elem_index_ensure(bm, BM_LOOP);

  if (preserve_clnor) {
    BLI_assert(bm->lnor_spacearr->lspacearr != NULL);

    BM_ITER_MESH (f, &fiter, bm, BM_FACES_OF_MESH) {
      BM_ITER_ELEM (l, &liter, f, BM_LOOPS_OF_FACE) {
        if (BM_ELEM_API_FLAG_TEST(l, BM_LNORSPACE_UPDATE) ||
            bm->spacearr_dirty & BM_SPACEARR_DIRTY_ALL) {
          short(*clnor)[2] = BM_ELEM_CD_GET_VOID_P(l, cd_loop_clnors_offset);
          int l_index = BM_elem_index_get(l);

          BKE_lnor_space_custom_data_to_normal(
              bm->lnor_spacearr->lspacearr[l_index], *clnor, oldnors[l_index]);
        }
      }
    }
  }

  if (bm->spacearr_dirty & BM_SPACEARR_DIRTY_ALL) {
    BKE_lnor_spacearr_clear(bm->lnor_spacearr);
  }
  BM_loops_calc_normal_vcos(bm,
                            NULL,
                            NULL,
                            NULL,
                            true,
                            M_PI,
                            r_lnors,
                            bm->lnor_spacearr,
                            NULL,
                            cd_loop_clnors_offset,
                            true);
  MEM_freeN(r_lnors);

  BM_ITER_MESH (f, &fiter, bm, BM_FACES_OF_MESH) {
    BM_ITER_ELEM (l, &liter, f, BM_LOOPS_OF_FACE) {
      if (BM_ELEM_API_FLAG_TEST(l, BM_LNORSPACE_UPDATE) ||
          bm->spacearr_dirty & BM_SPACEARR_DIRTY_ALL) {
        if (preserve_clnor) {
          short(*clnor)[2] = BM_ELEM_CD_GET_VOID_P(l, cd_loop_clnors_offset);
          int l_index = BM_elem_index_get(l);
          BKE_lnor_space_custom_normal_to_data(
              bm->lnor_spacearr->lspacearr[l_index], oldnors[l_index], *clnor);
        }
        BM_ELEM_API_FLAG_DISABLE(l, BM_LNORSPACE_UPDATE);
      }
    }
  }

  MEM_SAFE_FREE(oldnors);
  bm->spacearr_dirty &= ~(BM_SPACEARR_DIRTY | BM_SPACEARR_DIRTY_ALL);

#ifndef NDEBUG
  BM_lnorspace_err(bm);
#endif
}

void BM_lnorspace_update(BMesh *bm)
{
  if (bm->lnor_spacearr == NULL) {
    bm->lnor_spacearr = MEM_callocN(sizeof(*bm->lnor_spacearr), __func__);
  }
  if (bm->lnor_spacearr->lspacearr == NULL) {
    float(*lnors)[3] = MEM_callocN(sizeof(*lnors) * bm->totloop, __func__);

    BM_lnorspacearr_store(bm, lnors);

    MEM_freeN(lnors);
  }
  else if (bm->spacearr_dirty & (BM_SPACEARR_DIRTY | BM_SPACEARR_DIRTY_ALL)) {
    BM_lnorspace_rebuild(bm, false);
  }
}

void BM_normals_loops_edges_tag(BMesh *bm, const bool do_edges)
{
  BMFace *f;
  BMEdge *e;
  BMIter fiter, eiter;
  BMLoop *l_curr, *l_first;

  if (do_edges) {
    int index_edge;
    BM_ITER_MESH_INDEX (e, &eiter, bm, BM_EDGES_OF_MESH, index_edge) {
      BMLoop *l_a, *l_b;

      BM_elem_index_set(e, index_edge); /* set_inline */
      BM_elem_flag_disable(e, BM_ELEM_TAG);
      if (BM_edge_loop_pair(e, &l_a, &l_b)) {
        if (BM_elem_flag_test(e, BM_ELEM_SMOOTH) && l_a->v != l_b->v) {
          BM_elem_flag_enable(e, BM_ELEM_TAG);
        }
      }
    }
    bm->elem_index_dirty &= ~BM_EDGE;
  }

  int index_face, index_loop = 0;
  BM_ITER_MESH_INDEX (f, &fiter, bm, BM_FACES_OF_MESH, index_face) {
    BM_elem_index_set(f, index_face); /* set_inline */
    l_curr = l_first = BM_FACE_FIRST_LOOP(f);
    do {
      BM_elem_index_set(l_curr, index_loop++); /* set_inline */
      BM_elem_flag_disable(l_curr, BM_ELEM_TAG);
    } while ((l_curr = l_curr->next) != l_first);
  }
  bm->elem_index_dirty &= ~(BM_FACE | BM_LOOP);
}

/**
 * Auxiliary function only used by rebuild to detect if any spaces were not marked as invalid.
 * Reports error if any of the lnor spaces change after rebuilding, meaning that all the possible
 * lnor spaces to be rebuilt were not correctly marked.
 */
#ifndef NDEBUG
void BM_lnorspace_err(BMesh *bm)
{
  bm->spacearr_dirty |= BM_SPACEARR_DIRTY_ALL;
  bool clear = true;

  MLoopNorSpaceArray *temp = MEM_callocN(sizeof(*temp), __func__);
  temp->lspacearr = NULL;

  BKE_lnor_spacearr_init(temp, bm->totloop, MLNOR_SPACEARR_BMLOOP_PTR);

  int cd_loop_clnors_offset = CustomData_get_offset(&bm->ldata, CD_CUSTOMLOOPNORMAL);
  float(*lnors)[3] = MEM_callocN(sizeof(*lnors) * bm->totloop, __func__);
  BM_loops_calc_normal_vcos(
      bm, NULL, NULL, NULL, true, M_PI, lnors, temp, NULL, cd_loop_clnors_offset, true);

  for (int i = 0; i < bm->totloop; i++) {
    int j = 0;
    j += compare_ff(
        temp->lspacearr[i]->ref_alpha, bm->lnor_spacearr->lspacearr[i]->ref_alpha, 1e-4f);
    j += compare_ff(
        temp->lspacearr[i]->ref_beta, bm->lnor_spacearr->lspacearr[i]->ref_beta, 1e-4f);
    j += compare_v3v3(
        temp->lspacearr[i]->vec_lnor, bm->lnor_spacearr->lspacearr[i]->vec_lnor, 1e-4f);
    j += compare_v3v3(
        temp->lspacearr[i]->vec_ortho, bm->lnor_spacearr->lspacearr[i]->vec_ortho, 1e-4f);
    j += compare_v3v3(
        temp->lspacearr[i]->vec_ref, bm->lnor_spacearr->lspacearr[i]->vec_ref, 1e-4f);

    if (j != 5) {
      clear = false;
      break;
    }
  }
  BKE_lnor_spacearr_free(temp);
  MEM_freeN(temp);
  MEM_freeN(lnors);
  BLI_assert(clear);

  bm->spacearr_dirty &= ~BM_SPACEARR_DIRTY_ALL;
}
#endif

static void bm_loop_normal_mark_indiv_do_loop(BMLoop *l,
                                              BLI_bitmap *loops,
                                              MLoopNorSpaceArray *lnor_spacearr,
                                              int *totloopsel,
                                              const bool do_all_loops_of_vert)
{
  if (l != NULL) {
    const int l_idx = BM_elem_index_get(l);

    if (!BLI_BITMAP_TEST(loops, l_idx)) {
      /* If vert and face selected share a loop, mark it for editing. */
      BLI_BITMAP_ENABLE(loops, l_idx);
      (*totloopsel)++;

      if (do_all_loops_of_vert) {
        /* If required, also mark all loops shared by that vertex.
         * This is needed when loop spaces may change
         * (i.e. when some faces or edges might change of smooth/sharp status). */
        BMIter liter;
        BMLoop *lfan;
        BM_ITER_ELEM (lfan, &liter, l->v, BM_LOOPS_OF_VERT) {
          const int lfan_idx = BM_elem_index_get(lfan);
          if (!BLI_BITMAP_TEST(loops, lfan_idx)) {
            BLI_BITMAP_ENABLE(loops, lfan_idx);
            (*totloopsel)++;
          }
        }
      }
      else {
        /* Mark all loops in same loop normal space (aka smooth fan). */
        if ((lnor_spacearr->lspacearr[l_idx]->flags & MLNOR_SPACE_IS_SINGLE) == 0) {
          for (LinkNode *node = lnor_spacearr->lspacearr[l_idx]->loops; node; node = node->next) {
            const int lfan_idx = BM_elem_index_get((BMLoop *)node->link);
            if (!BLI_BITMAP_TEST(loops, lfan_idx)) {
              BLI_BITMAP_ENABLE(loops, lfan_idx);
              (*totloopsel)++;
            }
          }
        }
      }
    }
  }
}

/* Mark the individual clnors to be edited, if multiple selection methods are used. */
static int bm_loop_normal_mark_indiv(BMesh *bm, BLI_bitmap *loops, const bool do_all_loops_of_vert)
{
  BMEditSelection *ese, *ese_prev;
  int totloopsel = 0;

  const bool sel_verts = (bm->selectmode & SCE_SELECT_VERTEX) != 0;
  const bool sel_edges = (bm->selectmode & SCE_SELECT_EDGE) != 0;
  const bool sel_faces = (bm->selectmode & SCE_SELECT_FACE) != 0;
  const bool use_sel_face_history = sel_faces && (sel_edges || sel_verts);

  BM_mesh_elem_index_ensure(bm, BM_LOOP);

  BLI_assert(bm->lnor_spacearr != NULL);
  BLI_assert(bm->lnor_spacearr->data_type == MLNOR_SPACEARR_BMLOOP_PTR);

  if (use_sel_face_history) {
    /* Using face history allows to select a single loop from a single face...
     * Note that this is On² piece of code,
     * but it is not designed to be used with huge selection sets,
     * rather with only a few items selected at most.*/
    /* Goes from last selected to the first selected element. */
    for (ese = bm->selected.last; ese; ese = ese->prev) {
      if (ese->htype == BM_FACE) {
        /* If current face is selected,
         * then any verts to be edited must have been selected before it. */
        for (ese_prev = ese->prev; ese_prev; ese_prev = ese_prev->prev) {
          if (ese_prev->htype == BM_VERT) {
            bm_loop_normal_mark_indiv_do_loop(
                BM_face_vert_share_loop((BMFace *)ese->ele, (BMVert *)ese_prev->ele),
                loops,
                bm->lnor_spacearr,
                &totloopsel,
                do_all_loops_of_vert);
          }
          else if (ese_prev->htype == BM_EDGE) {
            BMEdge *e = (BMEdge *)ese_prev->ele;
            bm_loop_normal_mark_indiv_do_loop(BM_face_vert_share_loop((BMFace *)ese->ele, e->v1),
                                              loops,
                                              bm->lnor_spacearr,
                                              &totloopsel,
                                              do_all_loops_of_vert);

            bm_loop_normal_mark_indiv_do_loop(BM_face_vert_share_loop((BMFace *)ese->ele, e->v2),
                                              loops,
                                              bm->lnor_spacearr,
                                              &totloopsel,
                                              do_all_loops_of_vert);
          }
        }
      }
    }
  }
  else {
    if (sel_faces) {
      /* Only select all loops of selected faces. */
      BMLoop *l;
      BMFace *f;
      BMIter liter, fiter;
      BM_ITER_MESH (f, &fiter, bm, BM_FACES_OF_MESH) {
        if (BM_elem_flag_test(f, BM_ELEM_SELECT)) {
          BM_ITER_ELEM (l, &liter, f, BM_LOOPS_OF_FACE) {
            bm_loop_normal_mark_indiv_do_loop(
                l, loops, bm->lnor_spacearr, &totloopsel, do_all_loops_of_vert);
          }
        }
      }
    }
    if (sel_edges) {
      /* Only select all loops of selected edges. */
      BMLoop *l;
      BMEdge *e;
      BMIter liter, eiter;
      BM_ITER_MESH (e, &eiter, bm, BM_EDGES_OF_MESH) {
        if (BM_elem_flag_test(e, BM_ELEM_SELECT)) {
          BM_ITER_ELEM (l, &liter, e, BM_LOOPS_OF_EDGE) {
            bm_loop_normal_mark_indiv_do_loop(
                l, loops, bm->lnor_spacearr, &totloopsel, do_all_loops_of_vert);
            /* Loops actually 'have' two edges, or said otherwise, a selected edge actually selects
             * *two* loops in each of its faces. We have to find the other one too. */
            if (BM_vert_in_edge(e, l->next->v)) {
              bm_loop_normal_mark_indiv_do_loop(
                  l->next, loops, bm->lnor_spacearr, &totloopsel, do_all_loops_of_vert);
            }
            else {
              BLI_assert(BM_vert_in_edge(e, l->prev->v));
              bm_loop_normal_mark_indiv_do_loop(
                  l->prev, loops, bm->lnor_spacearr, &totloopsel, do_all_loops_of_vert);
            }
          }
        }
      }
    }
    if (sel_verts) {
      /* Select all loops of selected verts. */
      BMLoop *l;
      BMVert *v;
      BMIter liter, viter;
      BM_ITER_MESH (v, &viter, bm, BM_VERTS_OF_MESH) {
        if (BM_elem_flag_test(v, BM_ELEM_SELECT)) {
          BM_ITER_ELEM (l, &liter, v, BM_LOOPS_OF_VERT) {
            bm_loop_normal_mark_indiv_do_loop(
                l, loops, bm->lnor_spacearr, &totloopsel, do_all_loops_of_vert);
          }
        }
      }
    }
  }

  return totloopsel;
}

static void loop_normal_editdata_init(
    BMesh *bm, BMLoopNorEditData *lnor_ed, BMVert *v, BMLoop *l, const int offset)
{
  BLI_assert(bm->lnor_spacearr != NULL);
  BLI_assert(bm->lnor_spacearr->lspacearr != NULL);

  const int l_index = BM_elem_index_get(l);
  short *clnors_data = BM_ELEM_CD_GET_VOID_P(l, offset);

  lnor_ed->loop_index = l_index;
  lnor_ed->loop = l;

  float custom_normal[3];
  BKE_lnor_space_custom_data_to_normal(
      bm->lnor_spacearr->lspacearr[l_index], clnors_data, custom_normal);

  lnor_ed->clnors_data = clnors_data;
  copy_v3_v3(lnor_ed->nloc, custom_normal);
  copy_v3_v3(lnor_ed->niloc, custom_normal);

  lnor_ed->loc = v->co;
}

BMLoopNorEditDataArray *BM_loop_normal_editdata_array_init(BMesh *bm,
                                                           const bool do_all_loops_of_vert)
{
  BMLoop *l;
  BMVert *v;
  BMIter liter, viter;

  int totloopsel = 0;

  BLI_assert(bm->spacearr_dirty == 0);

  BMLoopNorEditDataArray *lnors_ed_arr = MEM_callocN(sizeof(*lnors_ed_arr), __func__);
  lnors_ed_arr->lidx_to_lnor_editdata = MEM_callocN(
      sizeof(*lnors_ed_arr->lidx_to_lnor_editdata) * bm->totloop, __func__);

  if (!CustomData_has_layer(&bm->ldata, CD_CUSTOMLOOPNORMAL)) {
    BM_data_layer_add(bm, &bm->ldata, CD_CUSTOMLOOPNORMAL);
  }
  const int cd_custom_normal_offset = CustomData_get_offset(&bm->ldata, CD_CUSTOMLOOPNORMAL);

  BM_mesh_elem_index_ensure(bm, BM_LOOP);

  BLI_bitmap *loops = BLI_BITMAP_NEW(bm->totloop, __func__);

  /* This function define loop normals to edit, based on selection modes and history. */
  totloopsel = bm_loop_normal_mark_indiv(bm, loops, do_all_loops_of_vert);

  if (totloopsel) {
    BMLoopNorEditData *lnor_ed = lnors_ed_arr->lnor_editdata = MEM_mallocN(
        sizeof(*lnor_ed) * totloopsel, __func__);

    BM_ITER_MESH (v, &viter, bm, BM_VERTS_OF_MESH) {
      BM_ITER_ELEM (l, &liter, v, BM_LOOPS_OF_VERT) {
        if (BLI_BITMAP_TEST(loops, BM_elem_index_get(l))) {
          loop_normal_editdata_init(bm, lnor_ed, v, l, cd_custom_normal_offset);
          lnors_ed_arr->lidx_to_lnor_editdata[BM_elem_index_get(l)] = lnor_ed;
          lnor_ed++;
        }
      }
    }
    lnors_ed_arr->totloop = totloopsel;
  }

  MEM_freeN(loops);
  lnors_ed_arr->cd_custom_normal_offset = cd_custom_normal_offset;
  return lnors_ed_arr;
}

void BM_loop_normal_editdata_array_free(BMLoopNorEditDataArray *lnors_ed_arr)
{
  MEM_SAFE_FREE(lnors_ed_arr->lnor_editdata);
  MEM_SAFE_FREE(lnors_ed_arr->lidx_to_lnor_editdata);
  MEM_freeN(lnors_ed_arr);
}

int BM_total_loop_select(BMesh *bm)
{
  int r_sel = 0;
  BMVert *v;
  BMIter viter;

  BM_ITER_MESH (v, &viter, bm, BM_VERTS_OF_MESH) {
    if (BM_elem_flag_test(v, BM_ELEM_SELECT)) {
      r_sel += BM_vert_face_count(v);
    }
  }
  return r_sel;
}

/**
 * \brief BMesh Begin Edit
 *
 * Functions for setting up a mesh for editing and cleaning up after
 * the editing operations are done. These are called by the tools/operator
 * API for each time a tool is executed.
 */
void bmesh_edit_begin(BMesh *UNUSED(bm), BMOpTypeFlag UNUSED(type_flag))
{
  /* Most operators seem to be using BMO_OPTYPE_FLAG_UNTAN_MULTIRES to change the MDisps to
   * absolute space during mesh edits. With this enabled, changes to the topology
   * (loop cuts, edge subdivides, etc) are not reflected in the higher levels of
   * the mesh at all, which doesn't seem right. Turning off completely for now,
   * until this is shown to be better for certain types of mesh edits. */
#ifdef BMOP_UNTAN_MULTIRES_ENABLED
  /* switch multires data out of tangent space */
  if ((type_flag & BMO_OPTYPE_FLAG_UNTAN_MULTIRES) &&
      CustomData_has_layer(&bm->ldata, CD_MDISPS)) {
    bmesh_mdisps_space_set(bm, MULTIRES_SPACE_TANGENT, MULTIRES_SPACE_ABSOLUTE);

    /* ensure correct normals, if possible */
    bmesh_rationalize_normals(bm, 0);
    BM_mesh_normals_update(bm);
  }
#endif
}

/**
 * \brief BMesh End Edit
 */
void bmesh_edit_end(BMesh *bm, BMOpTypeFlag type_flag)
{
  ListBase select_history;

  /* BMO_OPTYPE_FLAG_UNTAN_MULTIRES disabled for now, see comment above in bmesh_edit_begin. */
#ifdef BMOP_UNTAN_MULTIRES_ENABLED
  /* switch multires data into tangent space */
  if ((flag & BMO_OPTYPE_FLAG_UNTAN_MULTIRES) && CustomData_has_layer(&bm->ldata, CD_MDISPS)) {
    /* set normals to their previous winding */
    bmesh_rationalize_normals(bm, 1);
    bmesh_mdisps_space_set(bm, MULTIRES_SPACE_ABSOLUTE, MULTIRES_SPACE_TANGENT);
  }
  else if (flag & BMO_OP_FLAG_RATIONALIZE_NORMALS) {
    bmesh_rationalize_normals(bm, 1);
  }
#endif

  /* compute normals, clear temp flags and flush selections */
  if (type_flag & BMO_OPTYPE_FLAG_NORMALS_CALC) {
    bm->spacearr_dirty |= BM_SPACEARR_DIRTY_ALL;
    BM_mesh_normals_update(bm);
  }

  if ((type_flag & BMO_OPTYPE_FLAG_SELECT_VALIDATE) == 0) {
    select_history = bm->selected;
    BLI_listbase_clear(&bm->selected);
  }

  if (type_flag & BMO_OPTYPE_FLAG_SELECT_FLUSH) {
    BM_mesh_select_mode_flush(bm);
  }

  if ((type_flag & BMO_OPTYPE_FLAG_SELECT_VALIDATE) == 0) {
    bm->selected = select_history;
  }
  if (type_flag & BMO_OPTYPE_FLAG_INVALIDATE_CLNOR_ALL) {
    bm->spacearr_dirty |= BM_SPACEARR_DIRTY_ALL;
  }
}

void BM_mesh_elem_index_ensure_ex(BMesh *bm, const char htype, int elem_offset[4])
{

#ifdef DEBUG
  BM_ELEM_INDEX_VALIDATE(bm, "Should Never Fail!", __func__);
#endif

  if (elem_offset == NULL) {
    /* Simple case. */
    const char htype_needed = bm->elem_index_dirty & htype;
    if (htype_needed == 0) {
      goto finally;
    }
  }

  if (htype & BM_VERT) {
    if ((bm->elem_index_dirty & BM_VERT) || (elem_offset && elem_offset[0])) {
      BMIter iter;
      BMElem *ele;

      int index = elem_offset ? elem_offset[0] : 0;
      BM_ITER_MESH (ele, &iter, bm, BM_VERTS_OF_MESH) {
        BM_elem_index_set(ele, index++); /* set_ok */
      }
      BLI_assert(elem_offset || index == bm->totvert);
    }
    else {
      // printf("%s: skipping vert index calc!\n", __func__);
    }
  }

  if (htype & BM_EDGE) {
    if ((bm->elem_index_dirty & BM_EDGE) || (elem_offset && elem_offset[1])) {
      BMIter iter;
      BMElem *ele;

      int index = elem_offset ? elem_offset[1] : 0;
      BM_ITER_MESH (ele, &iter, bm, BM_EDGES_OF_MESH) {
        BM_elem_index_set(ele, index++); /* set_ok */
      }
      BLI_assert(elem_offset || index == bm->totedge);
    }
    else {
      // printf("%s: skipping edge index calc!\n", __func__);
    }
  }

  if (htype & (BM_FACE | BM_LOOP)) {
    if ((bm->elem_index_dirty & (BM_FACE | BM_LOOP)) ||
        (elem_offset && (elem_offset[2] || elem_offset[3]))) {
      BMIter iter;
      BMElem *ele;

      const bool update_face = (htype & BM_FACE) && (bm->elem_index_dirty & BM_FACE);
      const bool update_loop = (htype & BM_LOOP) && (bm->elem_index_dirty & BM_LOOP);

      int index_loop = elem_offset ? elem_offset[2] : 0;
      int index = elem_offset ? elem_offset[3] : 0;

      BM_ITER_MESH (ele, &iter, bm, BM_FACES_OF_MESH) {
        if (update_face) {
          BM_elem_index_set(ele, index++); /* set_ok */
        }

        if (update_loop) {
          BMLoop *l_iter, *l_first;

          l_iter = l_first = BM_FACE_FIRST_LOOP((BMFace *)ele);
          do {
            BM_elem_index_set(l_iter, index_loop++); /* set_ok */
          } while ((l_iter = l_iter->next) != l_first);
        }
      }

      BLI_assert(elem_offset || !update_face || index == bm->totface);
      if (update_loop) {
        BLI_assert(elem_offset || !update_loop || index_loop == bm->totloop);
      }
    }
    else {
      // printf("%s: skipping face/loop index calc!\n", __func__);
    }
  }

finally:
  bm->elem_index_dirty &= ~htype;
  if (elem_offset) {
    if (htype & BM_VERT) {
      elem_offset[0] += bm->totvert;
      if (elem_offset[0] != bm->totvert) {
        bm->elem_index_dirty |= BM_VERT;
      }
    }
    if (htype & BM_EDGE) {
      elem_offset[1] += bm->totedge;
      if (elem_offset[1] != bm->totedge) {
        bm->elem_index_dirty |= BM_EDGE;
      }
    }
    if (htype & BM_LOOP) {
      elem_offset[2] += bm->totloop;
      if (elem_offset[2] != bm->totloop) {
        bm->elem_index_dirty |= BM_LOOP;
      }
    }
    if (htype & BM_FACE) {
      elem_offset[3] += bm->totface;
      if (elem_offset[3] != bm->totface) {
        bm->elem_index_dirty |= BM_FACE;
      }
    }
  }
}

void BM_mesh_elem_index_ensure(BMesh *bm, const char htype)
{
  BM_mesh_elem_index_ensure_ex(bm, htype, NULL);
}

/**
 * Array checking/setting macros
 *
 * Currently vert/edge/loop/face index data is being abused, in a few areas of the code.
 *
 * To avoid correcting them afterwards, set 'bm->elem_index_dirty' however its possible
 * this flag is set incorrectly which could crash blender.
 *
 * Code that calls this functions may depend on dirty indices on being set.
 * Keep this function read-only.
 */

void BM_mesh_elem_index_validate(
    BMesh *bm, const char *location, const char *func, const char *msg_a, const char *msg_b)
{
  const char iter_types[3] = {BM_VERTS_OF_MESH, BM_EDGES_OF_MESH, BM_FACES_OF_MESH};

  const char flag_types[3] = {BM_VERT, BM_EDGE, BM_FACE};
  const char *type_names[3] = {"vert", "edge", "face"};

  BMIter iter;
  BMElem *ele;
  int i;
  bool is_any_error = 0;

  for (i = 0; i < 3; i++) {
    const bool is_dirty = (flag_types[i] & bm->elem_index_dirty) != 0;
    int index = 0;
    bool is_error = false;
    int err_val = 0;
    int err_idx = 0;

    BM_ITER_MESH (ele, &iter, bm, iter_types[i]) {
      if (!is_dirty) {
        if (BM_elem_index_get(ele) != index) {
          err_val = BM_elem_index_get(ele);
          err_idx = index;
          is_error = true;
          break;
        }
      }
      index++;
    }

    if ((is_error == true) && (is_dirty == false)) {
      is_any_error = true;
      fprintf(stderr,
              "Invalid Index: at %s, %s, %s[%d] invalid index %d, '%s', '%s'\n",
              location,
              func,
              type_names[i],
              err_idx,
              err_val,
              msg_a,
              msg_b);
    }
    else if ((is_error == false) && (is_dirty == true)) {

#if 0 /* mostly annoying */

      /* dirty may have been incorrectly set */
      fprintf(stderr,
              "Invalid Dirty: at %s, %s (%s), dirty flag was set but all index values are "
              "correct, '%s', '%s'\n",
              location,
              func,
              type_names[i],
              msg_a,
              msg_b);
#endif
    }
  }

#if 0 /* mostly annoying, even in debug mode */
#  ifdef DEBUG
  if (is_any_error == 0) {
    fprintf(stderr, "Valid Index Success: at %s, %s, '%s', '%s'\n", location, func, msg_a, msg_b);
  }
#  endif
#endif
  (void)is_any_error; /* shut up the compiler */
}

/* debug check only - no need to optimize */
#ifndef NDEBUG
bool BM_mesh_elem_table_check(BMesh *bm)
{
  BMIter iter;
  BMElem *ele;
  int i;

  if (bm->vtable && ((bm->elem_table_dirty & BM_VERT) == 0)) {
    BM_ITER_MESH_INDEX (ele, &iter, bm, BM_VERTS_OF_MESH, i) {
      if (ele != (BMElem *)bm->vtable[i]) {
        return false;
      }
    }
  }

  if (bm->etable && ((bm->elem_table_dirty & BM_EDGE) == 0)) {
    BM_ITER_MESH_INDEX (ele, &iter, bm, BM_EDGES_OF_MESH, i) {
      if (ele != (BMElem *)bm->etable[i]) {
        return false;
      }
    }
  }

  if (bm->ftable && ((bm->elem_table_dirty & BM_FACE) == 0)) {
    BM_ITER_MESH_INDEX (ele, &iter, bm, BM_FACES_OF_MESH, i) {
      if (ele != (BMElem *)bm->ftable[i]) {
        return false;
      }
    }
  }

  return true;
}
#endif

void BM_mesh_elem_table_ensure(BMesh *bm, const char htype)
{
  /* assume if the array is non-null then its valid and no need to recalc */
  const char htype_needed =
      (((bm->vtable && ((bm->elem_table_dirty & BM_VERT) == 0)) ? 0 : BM_VERT) |
       ((bm->etable && ((bm->elem_table_dirty & BM_EDGE) == 0)) ? 0 : BM_EDGE) |
       ((bm->ftable && ((bm->elem_table_dirty & BM_FACE) == 0)) ? 0 : BM_FACE)) &
      htype;

  BLI_assert((htype & ~BM_ALL_NOLOOP) == 0);

  /* in debug mode double check we didn't need to recalculate */
  BLI_assert(BM_mesh_elem_table_check(bm) == true);

  if (htype_needed == 0) {
    goto finally;
  }

  if (htype_needed & BM_VERT) {
    if (bm->vtable && bm->totvert <= bm->vtable_tot && bm->totvert * 2 >= bm->vtable_tot) {
      /* pass (re-use the array) */
    }
    else {
      if (bm->vtable) {
        MEM_freeN(bm->vtable);
      }
      bm->vtable = MEM_mallocN(sizeof(void **) * bm->totvert, "bm->vtable");
      bm->vtable_tot = bm->totvert;
    }
  }
  if (htype_needed & BM_EDGE) {
    if (bm->etable && bm->totedge <= bm->etable_tot && bm->totedge * 2 >= bm->etable_tot) {
      /* pass (re-use the array) */
    }
    else {
      if (bm->etable) {
        MEM_freeN(bm->etable);
      }
      bm->etable = MEM_mallocN(sizeof(void **) * bm->totedge, "bm->etable");
      bm->etable_tot = bm->totedge;
    }
  }
  if (htype_needed & BM_FACE) {
    if (bm->ftable && bm->totface <= bm->ftable_tot && bm->totface * 2 >= bm->ftable_tot) {
      /* pass (re-use the array) */
    }
    else {
      if (bm->ftable) {
        MEM_freeN(bm->ftable);
      }
      bm->ftable = MEM_mallocN(sizeof(void **) * bm->totface, "bm->ftable");
      bm->ftable_tot = bm->totface;
    }
  }

  if (htype_needed & BM_VERT) {
    BM_iter_as_array(bm, BM_VERTS_OF_MESH, NULL, (void **)bm->vtable, bm->totvert);
  }

  if (htype_needed & BM_EDGE) {
    BM_iter_as_array(bm, BM_EDGES_OF_MESH, NULL, (void **)bm->etable, bm->totedge);
  }

  if (htype_needed & BM_FACE) {
    BM_iter_as_array(bm, BM_FACES_OF_MESH, NULL, (void **)bm->ftable, bm->totface);
  }

finally:
  /* Only clear dirty flags when all the pointers and data are actually valid.
   * This prevents possible threading issues when dirty flag check failed but
   * data wasn't ready still.
   */
  bm->elem_table_dirty &= ~htype_needed;
}

/* use BM_mesh_elem_table_ensure where possible to avoid full rebuild */
void BM_mesh_elem_table_init(BMesh *bm, const char htype)
{
  BLI_assert((htype & ~BM_ALL_NOLOOP) == 0);

  /* force recalc */
  BM_mesh_elem_table_free(bm, BM_ALL_NOLOOP);
  BM_mesh_elem_table_ensure(bm, htype);
}

void BM_mesh_elem_table_free(BMesh *bm, const char htype)
{
  if (htype & BM_VERT) {
    MEM_SAFE_FREE(bm->vtable);
  }

  if (htype & BM_EDGE) {
    MEM_SAFE_FREE(bm->etable);
  }

  if (htype & BM_FACE) {
    MEM_SAFE_FREE(bm->ftable);
  }
}

BMVert *BM_vert_at_index_find(BMesh *bm, const int index)
{
  return BLI_mempool_findelem(bm->vpool, index);
}

BMEdge *BM_edge_at_index_find(BMesh *bm, const int index)
{
  return BLI_mempool_findelem(bm->epool, index);
}

BMFace *BM_face_at_index_find(BMesh *bm, const int index)
{
  return BLI_mempool_findelem(bm->fpool, index);
}

/**
 * Use lookup table when available, else use slower find functions.
 *
 * \note Try to use #BM_mesh_elem_table_ensure instead.
 */
BMVert *BM_vert_at_index_find_or_table(BMesh *bm, const int index)
{
  if ((bm->elem_table_dirty & BM_VERT) == 0) {
    return (index < bm->totvert) ? bm->vtable[index] : NULL;
  }
  else {
    return BM_vert_at_index_find(bm, index);
  }
}

BMEdge *BM_edge_at_index_find_or_table(BMesh *bm, const int index)
{
  if ((bm->elem_table_dirty & BM_EDGE) == 0) {
    return (index < bm->totedge) ? bm->etable[index] : NULL;
  }
  else {
    return BM_edge_at_index_find(bm, index);
  }
}

BMFace *BM_face_at_index_find_or_table(BMesh *bm, const int index)
{
  if ((bm->elem_table_dirty & BM_FACE) == 0) {
    return (index < bm->totface) ? bm->ftable[index] : NULL;
  }
  else {
    return BM_face_at_index_find(bm, index);
  }
}

/**
 * Return the amount of element of type 'type' in a given bmesh.
 */
int BM_mesh_elem_count(BMesh *bm, const char htype)
{
  BLI_assert((htype & ~BM_ALL_NOLOOP) == 0);

  switch (htype) {
    case BM_VERT:
      return bm->totvert;
    case BM_EDGE:
      return bm->totedge;
    case BM_FACE:
      return bm->totface;
    default: {
      BLI_assert(0);
      return 0;
    }
  }
}

/**
 * Remaps the vertices, edges and/or faces of the bmesh as indicated by vert/edge/face_idx arrays
 * (xxx_idx[org_index] = new_index).
 *
 * A NULL array means no changes.
 *
 * \note
 * - Does not mess with indices, just sets elem_index_dirty flag.
 * - For verts/edges/faces only (as loops must remain "ordered" and "aligned"
 *   on a per-face basis...).
 *
 * \warning Be careful if you keep pointers to affected BM elements,
 * or arrays, when using this func!
 */
void BM_mesh_remap(BMesh *bm, const uint *vert_idx, const uint *edge_idx, const uint *face_idx)
{
  /* Mapping old to new pointers. */
  GHash *vptr_map = NULL, *eptr_map = NULL, *fptr_map = NULL;
  BMIter iter, iterl;
  BMVert *ve;
  BMEdge *ed;
  BMFace *fa;
  BMLoop *lo;

  if (!(vert_idx || edge_idx || face_idx)) {
    return;
  }

  BM_mesh_elem_table_ensure(
      bm, (vert_idx ? BM_VERT : 0) | (edge_idx ? BM_EDGE : 0) | (face_idx ? BM_FACE : 0));

  /* Remap Verts */
  if (vert_idx) {
    BMVert **verts_pool, *verts_copy, **vep;
    int i, totvert = bm->totvert;
    const uint *new_idx;
    /* Special case: Python uses custom - data layers to hold PyObject references.
     * These have to be kept in - place, else the PyObject's we point to, wont point back to us. */
    const int cd_vert_pyptr = CustomData_get_offset(&bm->vdata, CD_BM_ELEM_PYPTR);

    /* Init the old-to-new vert pointers mapping */
    vptr_map = BLI_ghash_ptr_new_ex("BM_mesh_remap vert pointers mapping", bm->totvert);

    /* Make a copy of all vertices. */
    verts_pool = bm->vtable;
    verts_copy = MEM_mallocN(sizeof(BMVert) * totvert, "BM_mesh_remap verts copy");
    void **pyptrs = (cd_vert_pyptr != -1) ? MEM_mallocN(sizeof(void *) * totvert, __func__) : NULL;
    for (i = totvert, ve = verts_copy + totvert - 1, vep = verts_pool + totvert - 1; i--;
         ve--, vep--) {
      *ve = **vep;
      /*          printf("*vep: %p, verts_pool[%d]: %p\n", *vep, i, verts_pool[i]);*/
      if (cd_vert_pyptr != -1) {
        void **pyptr = BM_ELEM_CD_GET_VOID_P(((BMElem *)ve), cd_vert_pyptr);
        pyptrs[i] = *pyptr;
      }
    }

    /* Copy back verts to their new place, and update old2new pointers mapping. */
    new_idx = vert_idx + totvert - 1;
    ve = verts_copy + totvert - 1;
    vep = verts_pool + totvert - 1; /* old, org pointer */
    for (i = totvert; i--; new_idx--, ve--, vep--) {
      BMVert *new_vep = verts_pool[*new_idx];
      *new_vep = *ve;
#if 0
      printf(
          "mapping vert from %d to %d (%p/%p to %p)\n", i, *new_idx, *vep, verts_pool[i], new_vep);
#endif
      BLI_ghash_insert(vptr_map, *vep, new_vep);
      if (cd_vert_pyptr != -1) {
        void **pyptr = BM_ELEM_CD_GET_VOID_P(((BMElem *)new_vep), cd_vert_pyptr);
        *pyptr = pyptrs[*new_idx];
      }
    }
    bm->elem_index_dirty |= BM_VERT;
    bm->elem_table_dirty |= BM_VERT;

    MEM_freeN(verts_copy);
    if (pyptrs) {
      MEM_freeN(pyptrs);
    }
  }

  /* Remap Edges */
  if (edge_idx) {
    BMEdge **edges_pool, *edges_copy, **edp;
    int i, totedge = bm->totedge;
    const uint *new_idx;
    /* Special case: Python uses custom - data layers to hold PyObject references.
     * These have to be kept in - place, else the PyObject's we point to, wont point back to us. */
    const int cd_edge_pyptr = CustomData_get_offset(&bm->edata, CD_BM_ELEM_PYPTR);

    /* Init the old-to-new vert pointers mapping */
    eptr_map = BLI_ghash_ptr_new_ex("BM_mesh_remap edge pointers mapping", bm->totedge);

    /* Make a copy of all vertices. */
    edges_pool = bm->etable;
    edges_copy = MEM_mallocN(sizeof(BMEdge) * totedge, "BM_mesh_remap edges copy");
    void **pyptrs = (cd_edge_pyptr != -1) ? MEM_mallocN(sizeof(void *) * totedge, __func__) : NULL;
    for (i = totedge, ed = edges_copy + totedge - 1, edp = edges_pool + totedge - 1; i--;
         ed--, edp--) {
      *ed = **edp;
      if (cd_edge_pyptr != -1) {
        void **pyptr = BM_ELEM_CD_GET_VOID_P(((BMElem *)ed), cd_edge_pyptr);
        pyptrs[i] = *pyptr;
      }
    }

    /* Copy back verts to their new place, and update old2new pointers mapping. */
    new_idx = edge_idx + totedge - 1;
    ed = edges_copy + totedge - 1;
    edp = edges_pool + totedge - 1; /* old, org pointer */
    for (i = totedge; i--; new_idx--, ed--, edp--) {
      BMEdge *new_edp = edges_pool[*new_idx];
      *new_edp = *ed;
      BLI_ghash_insert(eptr_map, *edp, new_edp);
#if 0
      printf(
          "mapping edge from %d to %d (%p/%p to %p)\n", i, *new_idx, *edp, edges_pool[i], new_edp);
#endif
      if (cd_edge_pyptr != -1) {
        void **pyptr = BM_ELEM_CD_GET_VOID_P(((BMElem *)new_edp), cd_edge_pyptr);
        *pyptr = pyptrs[*new_idx];
      }
    }
    bm->elem_index_dirty |= BM_EDGE;
    bm->elem_table_dirty |= BM_EDGE;

    MEM_freeN(edges_copy);
    if (pyptrs) {
      MEM_freeN(pyptrs);
    }
  }

  /* Remap Faces */
  if (face_idx) {
    BMFace **faces_pool, *faces_copy, **fap;
    int i, totface = bm->totface;
    const uint *new_idx;
    /* Special case: Python uses custom - data layers to hold PyObject references.
     * These have to be kept in - place, else the PyObject's we point to, wont point back to us. */
    const int cd_poly_pyptr = CustomData_get_offset(&bm->pdata, CD_BM_ELEM_PYPTR);

    /* Init the old-to-new vert pointers mapping */
    fptr_map = BLI_ghash_ptr_new_ex("BM_mesh_remap face pointers mapping", bm->totface);

    /* Make a copy of all vertices. */
    faces_pool = bm->ftable;
    faces_copy = MEM_mallocN(sizeof(BMFace) * totface, "BM_mesh_remap faces copy");
    void **pyptrs = (cd_poly_pyptr != -1) ? MEM_mallocN(sizeof(void *) * totface, __func__) : NULL;
    for (i = totface, fa = faces_copy + totface - 1, fap = faces_pool + totface - 1; i--;
         fa--, fap--) {
      *fa = **fap;
      if (cd_poly_pyptr != -1) {
        void **pyptr = BM_ELEM_CD_GET_VOID_P(((BMElem *)fa), cd_poly_pyptr);
        pyptrs[i] = *pyptr;
      }
    }

    /* Copy back verts to their new place, and update old2new pointers mapping. */
    new_idx = face_idx + totface - 1;
    fa = faces_copy + totface - 1;
    fap = faces_pool + totface - 1; /* old, org pointer */
    for (i = totface; i--; new_idx--, fa--, fap--) {
      BMFace *new_fap = faces_pool[*new_idx];
      *new_fap = *fa;
      BLI_ghash_insert(fptr_map, *fap, new_fap);
      if (cd_poly_pyptr != -1) {
        void **pyptr = BM_ELEM_CD_GET_VOID_P(((BMElem *)new_fap), cd_poly_pyptr);
        *pyptr = pyptrs[*new_idx];
      }
    }

    bm->elem_index_dirty |= BM_FACE | BM_LOOP;
    bm->elem_table_dirty |= BM_FACE;

    MEM_freeN(faces_copy);
    if (pyptrs) {
      MEM_freeN(pyptrs);
    }
  }

  /* And now, fix all vertices/edges/faces/loops pointers! */
  /* Verts' pointers, only edge pointers... */
  if (eptr_map) {
    BM_ITER_MESH (ve, &iter, bm, BM_VERTS_OF_MESH) {
      /*          printf("Vert e: %p -> %p\n", ve->e, BLI_ghash_lookup(eptr_map, ve->e));*/
      if (ve->e) {
        ve->e = BLI_ghash_lookup(eptr_map, ve->e);
        BLI_assert(ve->e);
      }
    }
  }

  /* Edges' pointers, only vert pointers (as we don't mess with loops!),
   * and - ack! - edge pointers,
   * as we have to handle disklinks... */
  if (vptr_map || eptr_map) {
    BM_ITER_MESH (ed, &iter, bm, BM_EDGES_OF_MESH) {
      if (vptr_map) {
        /* printf("Edge v1: %p -> %p\n", ed->v1, BLI_ghash_lookup(vptr_map, ed->v1));*/
        /* printf("Edge v2: %p -> %p\n", ed->v2, BLI_ghash_lookup(vptr_map, ed->v2));*/
        ed->v1 = BLI_ghash_lookup(vptr_map, ed->v1);
        ed->v2 = BLI_ghash_lookup(vptr_map, ed->v2);
        BLI_assert(ed->v1);
        BLI_assert(ed->v2);
      }
      if (eptr_map) {
        /* printf("Edge v1_disk_link prev: %p -> %p\n", ed->v1_disk_link.prev,*/
        /*        BLI_ghash_lookup(eptr_map, ed->v1_disk_link.prev));*/
        /* printf("Edge v1_disk_link next: %p -> %p\n", ed->v1_disk_link.next,*/
        /*        BLI_ghash_lookup(eptr_map, ed->v1_disk_link.next));*/
        /* printf("Edge v2_disk_link prev: %p -> %p\n", ed->v2_disk_link.prev,*/
        /*        BLI_ghash_lookup(eptr_map, ed->v2_disk_link.prev));*/
        /* printf("Edge v2_disk_link next: %p -> %p\n", ed->v2_disk_link.next,*/
        /*        BLI_ghash_lookup(eptr_map, ed->v2_disk_link.next));*/
        ed->v1_disk_link.prev = BLI_ghash_lookup(eptr_map, ed->v1_disk_link.prev);
        ed->v1_disk_link.next = BLI_ghash_lookup(eptr_map, ed->v1_disk_link.next);
        ed->v2_disk_link.prev = BLI_ghash_lookup(eptr_map, ed->v2_disk_link.prev);
        ed->v2_disk_link.next = BLI_ghash_lookup(eptr_map, ed->v2_disk_link.next);
        BLI_assert(ed->v1_disk_link.prev);
        BLI_assert(ed->v1_disk_link.next);
        BLI_assert(ed->v2_disk_link.prev);
        BLI_assert(ed->v2_disk_link.next);
      }
    }
  }

  /* Faces' pointers (loops, in fact), always needed... */
  BM_ITER_MESH (fa, &iter, bm, BM_FACES_OF_MESH) {
    BM_ITER_ELEM (lo, &iterl, fa, BM_LOOPS_OF_FACE) {
      if (vptr_map) {
        /*              printf("Loop v: %p -> %p\n", lo->v, BLI_ghash_lookup(vptr_map, lo->v));*/
        lo->v = BLI_ghash_lookup(vptr_map, lo->v);
        BLI_assert(lo->v);
      }
      if (eptr_map) {
        /*              printf("Loop e: %p -> %p\n", lo->e, BLI_ghash_lookup(eptr_map, lo->e));*/
        lo->e = BLI_ghash_lookup(eptr_map, lo->e);
        BLI_assert(lo->e);
      }
      if (fptr_map) {
        /*              printf("Loop f: %p -> %p\n", lo->f, BLI_ghash_lookup(fptr_map, lo->f));*/
        lo->f = BLI_ghash_lookup(fptr_map, lo->f);
        BLI_assert(lo->f);
      }
    }
  }

  /* Selection history */
  {
    BMEditSelection *ese;
    for (ese = bm->selected.first; ese; ese = ese->next) {
      switch (ese->htype) {
        case BM_VERT:
          if (vptr_map) {
            ese->ele = BLI_ghash_lookup(vptr_map, ese->ele);
            BLI_assert(ese->ele);
          }
          break;
        case BM_EDGE:
          if (eptr_map) {
            ese->ele = BLI_ghash_lookup(eptr_map, ese->ele);
            BLI_assert(ese->ele);
          }
          break;
        case BM_FACE:
          if (fptr_map) {
            ese->ele = BLI_ghash_lookup(fptr_map, ese->ele);
            BLI_assert(ese->ele);
          }
          break;
      }
    }
  }

  if (fptr_map) {
    if (bm->act_face) {
      bm->act_face = BLI_ghash_lookup(fptr_map, bm->act_face);
      BLI_assert(bm->act_face);
    }
  }

  if (vptr_map) {
    BLI_ghash_free(vptr_map, NULL, NULL);
  }
  if (eptr_map) {
    BLI_ghash_free(eptr_map, NULL, NULL);
  }
  if (fptr_map) {
    BLI_ghash_free(fptr_map, NULL, NULL);
  }
}

/**
 * Use new memory pools for this mesh.
 *
 * \note needed for re-sizing elements (adding/removing tool flags)
 * but could also be used for packing fragmented bmeshes.
 */
void BM_mesh_rebuild(BMesh *bm,
                     const struct BMeshCreateParams *params,
                     BLI_mempool *vpool_dst,
                     BLI_mempool *epool_dst,
                     BLI_mempool *lpool_dst,
                     BLI_mempool *fpool_dst)
{
  const char remap = (vpool_dst ? BM_VERT : 0) | (epool_dst ? BM_EDGE : 0) |
                     (lpool_dst ? BM_LOOP : 0) | (fpool_dst ? BM_FACE : 0);

  BMVert **vtable_dst = (remap & BM_VERT) ? MEM_mallocN(bm->totvert * sizeof(BMVert *), __func__) :
                                            NULL;
  BMEdge **etable_dst = (remap & BM_EDGE) ? MEM_mallocN(bm->totedge * sizeof(BMEdge *), __func__) :
                                            NULL;
  BMLoop **ltable_dst = (remap & BM_LOOP) ? MEM_mallocN(bm->totloop * sizeof(BMLoop *), __func__) :
                                            NULL;
  BMFace **ftable_dst = (remap & BM_FACE) ? MEM_mallocN(bm->totface * sizeof(BMFace *), __func__) :
                                            NULL;

  const bool use_toolflags = params->use_toolflags;

  if (remap & BM_VERT) {
    BMIter iter;
    int index;
    BMVert *v_src;
    BM_ITER_MESH_INDEX (v_src, &iter, bm, BM_VERTS_OF_MESH, index) {
      BMVert *v_dst = BLI_mempool_alloc(vpool_dst);
      memcpy(v_dst, v_src, sizeof(BMVert));
      if (use_toolflags) {
        ((BMVert_OFlag *)v_dst)->oflags = bm->vtoolflagpool ?
                                              BLI_mempool_calloc(bm->vtoolflagpool) :
                                              NULL;
      }

      vtable_dst[index] = v_dst;
      BM_elem_index_set(v_src, index); /* set_ok */
    }
  }

  if (remap & BM_EDGE) {
    BMIter iter;
    int index;
    BMEdge *e_src;
    BM_ITER_MESH_INDEX (e_src, &iter, bm, BM_EDGES_OF_MESH, index) {
      BMEdge *e_dst = BLI_mempool_alloc(epool_dst);
      memcpy(e_dst, e_src, sizeof(BMEdge));
      if (use_toolflags) {
        ((BMEdge_OFlag *)e_dst)->oflags = bm->etoolflagpool ?
                                              BLI_mempool_calloc(bm->etoolflagpool) :
                                              NULL;
      }

      etable_dst[index] = e_dst;
      BM_elem_index_set(e_src, index); /* set_ok */
    }
  }

  if (remap & (BM_LOOP | BM_FACE)) {
    BMIter iter;
    int index, index_loop = 0;
    BMFace *f_src;
    BM_ITER_MESH_INDEX (f_src, &iter, bm, BM_FACES_OF_MESH, index) {

      if (remap & BM_FACE) {
        BMFace *f_dst = BLI_mempool_alloc(fpool_dst);
        memcpy(f_dst, f_src, sizeof(BMFace));
        if (use_toolflags) {
          ((BMFace_OFlag *)f_dst)->oflags = bm->ftoolflagpool ?
                                                BLI_mempool_calloc(bm->ftoolflagpool) :
                                                NULL;
        }

        ftable_dst[index] = f_dst;
        BM_elem_index_set(f_src, index); /* set_ok */
      }

      /* handle loops */
      if (remap & BM_LOOP) {
        BMLoop *l_iter_src, *l_first_src;
        l_iter_src = l_first_src = BM_FACE_FIRST_LOOP((BMFace *)f_src);
        do {
          BMLoop *l_dst = BLI_mempool_alloc(lpool_dst);
          memcpy(l_dst, l_iter_src, sizeof(BMLoop));
          ltable_dst[index_loop] = l_dst;
          BM_elem_index_set(l_iter_src, index_loop++); /* set_ok */
        } while ((l_iter_src = l_iter_src->next) != l_first_src);
      }
    }
  }

#define MAP_VERT(ele) vtable_dst[BM_elem_index_get(ele)]
#define MAP_EDGE(ele) etable_dst[BM_elem_index_get(ele)]
#define MAP_LOOP(ele) ltable_dst[BM_elem_index_get(ele)]
#define MAP_FACE(ele) ftable_dst[BM_elem_index_get(ele)]

#define REMAP_VERT(ele) \
  { \
    if (remap & BM_VERT) { \
      ele = MAP_VERT(ele); \
    } \
  } \
  ((void)0)
#define REMAP_EDGE(ele) \
  { \
    if (remap & BM_EDGE) { \
      ele = MAP_EDGE(ele); \
    } \
  } \
  ((void)0)
#define REMAP_LOOP(ele) \
  { \
    if (remap & BM_LOOP) { \
      ele = MAP_LOOP(ele); \
    } \
  } \
  ((void)0)
#define REMAP_FACE(ele) \
  { \
    if (remap & BM_FACE) { \
      ele = MAP_FACE(ele); \
    } \
  } \
  ((void)0)

  /* verts */
  {
    for (int i = 0; i < bm->totvert; i++) {
      BMVert *v = vtable_dst[i];
      if (v->e) {
        REMAP_EDGE(v->e);
      }
    }
  }

  /* edges */
  {
    for (int i = 0; i < bm->totedge; i++) {
      BMEdge *e = etable_dst[i];
      REMAP_VERT(e->v1);
      REMAP_VERT(e->v2);
      REMAP_EDGE(e->v1_disk_link.next);
      REMAP_EDGE(e->v1_disk_link.prev);
      REMAP_EDGE(e->v2_disk_link.next);
      REMAP_EDGE(e->v2_disk_link.prev);
      if (e->l) {
        REMAP_LOOP(e->l);
      }
    }
  }

  /* faces */
  {
    for (int i = 0; i < bm->totface; i++) {
      BMFace *f = ftable_dst[i];
      REMAP_LOOP(f->l_first);

      {
        BMLoop *l_iter, *l_first;
        l_iter = l_first = BM_FACE_FIRST_LOOP((BMFace *)f);
        do {
          REMAP_VERT(l_iter->v);
          REMAP_EDGE(l_iter->e);
          REMAP_FACE(l_iter->f);

          REMAP_LOOP(l_iter->radial_next);
          REMAP_LOOP(l_iter->radial_prev);
          REMAP_LOOP(l_iter->next);
          REMAP_LOOP(l_iter->prev);
        } while ((l_iter = l_iter->next) != l_first);
      }
    }
  }

  for (BMEditSelection *ese = bm->selected.first; ese; ese = ese->next) {
    switch (ese->htype) {
      case BM_VERT:
        if (remap & BM_VERT) {
          ese->ele = (BMElem *)MAP_VERT(ese->ele);
        }
        break;
      case BM_EDGE:
        if (remap & BM_EDGE) {
          ese->ele = (BMElem *)MAP_EDGE(ese->ele);
        }
        break;
      case BM_FACE:
        if (remap & BM_FACE) {
          ese->ele = (BMElem *)MAP_FACE(ese->ele);
        }
        break;
    }
  }

  if (bm->act_face) {
    REMAP_FACE(bm->act_face);
  }

#undef MAP_VERT
#undef MAP_EDGE
#undef MAP_LOOP
#undef MAP_EDGE

#undef REMAP_VERT
#undef REMAP_EDGE
#undef REMAP_LOOP
#undef REMAP_EDGE

  /* Cleanup, re-use local tables if the current mesh had tables allocated.
   * could use irrespective but it may use more memory then the caller wants
   * (and not be needed). */
  if (remap & BM_VERT) {
    if (bm->vtable) {
      SWAP(BMVert **, vtable_dst, bm->vtable);
      bm->vtable_tot = bm->totvert;
      bm->elem_table_dirty &= ~BM_VERT;
    }
    MEM_freeN(vtable_dst);
    BLI_mempool_destroy(bm->vpool);
    bm->vpool = vpool_dst;
  }

  if (remap & BM_EDGE) {
    if (bm->etable) {
      SWAP(BMEdge **, etable_dst, bm->etable);
      bm->etable_tot = bm->totedge;
      bm->elem_table_dirty &= ~BM_EDGE;
    }
    MEM_freeN(etable_dst);
    BLI_mempool_destroy(bm->epool);
    bm->epool = epool_dst;
  }

  if (remap & BM_LOOP) {
    /* no loop table */
    MEM_freeN(ltable_dst);
    BLI_mempool_destroy(bm->lpool);
    bm->lpool = lpool_dst;
  }

  if (remap & BM_FACE) {
    if (bm->ftable) {
      SWAP(BMFace **, ftable_dst, bm->ftable);
      bm->ftable_tot = bm->totface;
      bm->elem_table_dirty &= ~BM_FACE;
    }
    MEM_freeN(ftable_dst);
    BLI_mempool_destroy(bm->fpool);
    bm->fpool = fpool_dst;
  }
}

/**
 * Re-allocates mesh data with/without toolflags.
 */
void BM_mesh_toolflags_set(BMesh *bm, bool use_toolflags)
{
  if (bm->use_toolflags == use_toolflags) {
    return;
  }

  const BMAllocTemplate allocsize = BMALLOC_TEMPLATE_FROM_BM(bm);

  BLI_mempool *vpool_dst = NULL;
  BLI_mempool *epool_dst = NULL;
  BLI_mempool *fpool_dst = NULL;

  bm_mempool_init_ex(&allocsize, use_toolflags, &vpool_dst, &epool_dst, NULL, &fpool_dst);

  if (use_toolflags == false) {
    BLI_mempool_destroy(bm->vtoolflagpool);
    BLI_mempool_destroy(bm->etoolflagpool);
    BLI_mempool_destroy(bm->ftoolflagpool);

    bm->vtoolflagpool = NULL;
    bm->etoolflagpool = NULL;
    bm->ftoolflagpool = NULL;
  }

  BM_mesh_rebuild(bm,
                  &((struct BMeshCreateParams){
                      .use_toolflags = use_toolflags,
                  }),
                  vpool_dst,
                  epool_dst,
                  NULL,
                  fpool_dst);

  bm->use_toolflags = use_toolflags;
}

/* -------------------------------------------------------------------- */
/** \name BMesh Coordinate Access
 * \{ */

void BM_mesh_vert_coords_get(BMesh *bm, float (*vert_coords)[3])
{
  BMIter iter;
  BMVert *v;
  int i;
  BM_ITER_MESH_INDEX (v, &iter, bm, BM_VERTS_OF_MESH, i) {
    copy_v3_v3(vert_coords[i], v->co);
  }
}

float (*BM_mesh_vert_coords_alloc(BMesh *bm, int *r_vert_len))[3]
{
  float(*vert_coords)[3] = MEM_mallocN(bm->totvert * sizeof(*vert_coords), __func__);
  BM_mesh_vert_coords_get(bm, vert_coords);
  *r_vert_len = bm->totvert;
  return vert_coords;
}

void BM_mesh_vert_coords_apply(BMesh *bm, const float (*vert_coords)[3])
{
  BMIter iter;
  BMVert *v;
  int i;
  BM_ITER_MESH_INDEX (v, &iter, bm, BM_VERTS_OF_MESH, i) {
    copy_v3_v3(v->co, vert_coords[i]);
  }
}

void BM_mesh_vert_coords_apply_with_mat4(BMesh *bm,
                                         const float (*vert_coords)[3],
                                         const float mat[4][4])
{
  BMIter iter;
  BMVert *v;
  int i;
  BM_ITER_MESH_INDEX (v, &iter, bm, BM_VERTS_OF_MESH, i) {
    mul_v3_m4v3(v->co, mat, vert_coords[i]);
  }
}

/** \} */
